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The Pyrrho Book - The Pyrrho DBMS

1. CREATE FUNCTION GATHER1 RETURNS CHAR BEGIN DECLARE C CURSOR FOR SELECT A2 FROM A DECLARE DONE BOOLEAN DEFAULT FALSE DECLARE CONTINUE HANDLER FOR SQLSTATE 02000 SET DONE TRUE DECLARE A CHAR DEFAULT DECLARE P CHAR OPEN C 114 The Pyrrho Book May 2015 REPEAT FETCH INTO P IF NOT DONE THEN IF A THEN SET A P ELSE SET A A II P END IF END IF UNTIL DONE END REPEAT CLOSE C RETURN A BEGIN TRANSACTION drop function BankTransfer int int int CREATE FUNCTION BankTransfer IN fromAcct INT IN toAcct INT IN amount INT RETURNS VARCHAR 100 BEGIN DECLARE msg VARCHAR 100 DECLARE NOT FOUND BOOLEAN DEFAULT FALSE DECLARE CONTINUE HANDLER FOR SOLSTATE 02000 SET NOT FOUND TRUE SET msg ok UPDATE Accounts SET balance balance amount WHERE acctID fromAcct IF NOT FOUND THEN SET msg Unknown from account CAST fromAcct AS VARCHAR 10 E iS E BEGIN UPDATE Accounts SET balance balance amount WHERE acctID toAcct IF NOT FOUND THEN SET msg Unk
2. Billa EM Command Prompt PyrrhoCmd p 5434 _ TE x Fite Home Share View E DATA E gt AN Fie Home Share View E DATA E gt B Name Date modif D2 osp 30 03 2015 Osp 3 2015 The credentials supplied must be sufficient to create or open database D2 on server B and create objects in D2 In general partition changes need several changes to the _Partition table and changes need to be batched together in transactions of one of the following four kinds NewSegments DeleteSegments MoveSegments SplitSegment Close the session with C A5 4 Examine the database and partition At first sight it seems that the database on D is unchanged PyrrhoCmd p 5434 D table E as table E still appears to have the same two rows as its contents partitioning is transparent But if we look at table Sys Table we see that there now only one row in table E on this server 163 The Pyrrho Book May 2015 And if we look at the Log file table Logs we will see that the second entry in table E the record for Two has been deleted 127 0 0 1 5434 974 127 0 0 1 5435 In fact it has been moved to the new partition D2 on B as we requested Close reading of the PTransaction record shows that this actually a distributed transaction involving the configuration file and the partition The previous entries in the Logs file record the setting up of database D the
3. Command Prompt PyrrhoCmd p 5434 D Home Share View 0 H DATA E A SP 434 D Name D osp insert into E values 1 One insert into E values 2 Two table E table Log Use C control C to end the session 161 The Pyrrho Book May 2015 EX Command Prompt O X E VOSP gt PyrrhoCmd p 5434 D SQL gt create table E F int G char primary key F G SQL gt insert into E values 1 One SQL gt insert into E values 2 Two 5 PRole D 30 PUser asusrog Student 50 PTransaction for 6 Role 5 User 30 Time 30 03 2015 21 17 59 PTransaction 66 PTable E PTable 66 172 PDomain INTEGER PDomain 172 94 PColumn F for 66 0 72 PColumn3 94 112 PDomain CHAR PDomain 112 130 PColumn G for 66 1 112 PColumn3 130 149 PIndex U 51 on 66 94 130 PrimaryKey PIndex 149 1172 PTransaction for 1 Role 5 User 30 Time 30 03 2015 21 18 18 PTransaction o l188 Record for 66 94 1 130 One Record 188 210 PTransaction for 1 Role 5 User 30 Time 30 03 2015 21 18 18 PTransaction 1226 Record for 66 94 2 130 Two Record There is of course nothing special about this log file but things get more interesting soon Still on A create the configuration database PyrrhoCmd p 5434 _ This will create a configuration database on A with autocreated tables Client Database and _Partition in the configuration database as soon as we do something
4. Bi A Command Prompt PyrrhoCmd p 5434 _ Home Share view EQ PColumn G for 66 1 112 PColumn3 EEZ 149 PIndex U 51 on 66 94 130 PrimaryKey PIndex 149 E DATA Es fil 172 PTransaction for 1 Role 5 User 30 Time 30 03 2015 21 18 18 PTransaction ii 188 Record for 66 94 1 130 One Record 188 210 PTransaction for 1 Role 5 User 30 Time 30 03 2015 21 18 18 PTransaction 1226 Record for 66 94 2 130 Two Record E OSP gt PyrrhoCmd p SQL gt Now at the SQL gt prompt define a new partition D2 on B containing a single table segment E2 as follows Note the command is rather long for one line so enclose it in and note the gt prompts when you take a new line insert into _Partition values D2 127 0 0 1 5435 Student password D 127 0 0 1 5434 password E E2 F 2 2 true true For the full details of all of the columns in the _ Partition table see the manual But reading it from left to right this says Create a new segment in a partition called D2 on server B using these credentials whose base partition is D on server A partitioning table E with a segment called E2 containing rows where column F has values from 2 to 2 including both ends of this range 162 The Pyrrho Book May 2015 Note in the file browsers the creation not only of A _ osp by the command line but the creation of the new partition D2 and another configuration file on B
5. 108 The Pyrrho Book May 2015 COMMIT Let s first implement the DUAL table like in Oracle for single line info queries I ve since included the from static trick in Pyrrho BEGIN TRANSACTION CREATE TABLE DUAL c INT NOT NULL PRIMARY KEY CHECK c 1 INSERT INTO DUAL VALUES 1 S ELECT CURRENT DATE FROM DUAL OMMIT BEGIN TRANSACTION INSERT INTO T id s VALUES 2 Error test starts here division by zero should fail SELECT 1 0 AS dummy FROM DUAL COMMIT BEGIN TRANSACTION updating an non existing row UPDATE T SET s foo WHERE id 9999 I ve since included the 0 records message only very recently didn t regard this as an error at all Very reluctantly implemented the NOT_FOUND handler in stored procedures for this situation deleting an non existing row DELETE FROM T WHERE ida 7777 BEGIN TRANSACTION INSERT INTO T id s VALUES 2 Error test starts here INSERT INTO T id s VALUES 2 Hi I am a duplicate BEGIN TRANSACTION INSERT INTO T id s VALUES 3 how about inserting too long string value INSERT INTO T id s si VALUES 4 Integer overflow 9223372036854775808 INSERT INTO T id s VALUES 5 Testing an INSERT after errors SELE
6. EM Command Prompt osp T p 5434 d A s 0 S 0 M 0 El Home Share View o t E DATA E gt A Name D osp The next step is to create the configuration file on server B which had many side effects PyrrhoCmd p 5435 _ 131 The Pyrrho Book May 2015 EX Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d B p 5435 s 0 S 0 M 0 for er to t g OSP p S 0 M 0 D Ente S 0 0 Enter to start up C e and University of the West of Scotland hodb com MS protocol on 127 0 0 1 5435 se folder onnection 1 Files _ User EM Command Prompt PyrrhoCmd p 5435 _ Home Share View rhoCmd p 5434 D table E F int primary 4 E DATA E A i t into E values 4 7 The screenshot shows server B has received the connection information connection 1 on server B to database _ However the database is not actually opened until a transaction begins This happens when the user requests the insertion of a record into the _Database table or when an explicit transaction starts insert into _Database values D 127 0 0 1 5435 4 password 127 0 0 1 5434 Student password f the West of Scotland 4 Enter to start Home Share View t H DATA E A word 127 0 0 1 5434 Student D osp t E DATA E B Osp 132 The Pyrrho Book May 2015 We see that the new
7. Timestamp 128413241 Dombey amp Son 1488 Insert 1444 237 057 2007 14 1512 Nicholas Nickleby 1523 Insert 1488 123 05 2007 14 1513 Nostromo 1583 Insert 1539 123 05 2007 z H iHeart of Darkness 1634 Update i405 123 05 2007 Dombey and Son 1657 Delete 488 123 05 2007 Nostromo 23 05 2807 14 1511 The LogS table gives a semi readable account of all transactions 55 The Pyrrho Book May 2015 EN Command Prompt PyrrhoCmd SQL gt select Pos Desc from Log5 P Authority Temp Database Creation PUser TORE Malcolm tPTransaction for 6 Auth 4 User 32 Time 23 05 2807 19 12 18 PTable AUTHOR PDomain INTEGER INTEGER scale B8 PDomain CHARCB gt UCS CHAR A scale 0 1122 PColumn ID lt M gt 76 Idefault 1137 PIlndex U lt 5B gt on 65 122 gt PrimaryKey 1157 PColumn ANAME lt 1 gt 98 Idefault 1176 PTransaction for 2 Auth 4 User 32 Time 23 05 2667 19 12 51 1192 Record for 65 122 1 gt lt 157 Charles Dickens gt 1226 Record for 65 lt 1221 2 gt lt 157 Joseph Conrad gt 1258 iPTransaction for 6 Auth 4 User 32 ETA EA 19 13 25 1274 PTable BOOK 1284 PColumn ID gt 76 Idefault 361 Plndex UC51 gt on 274 284 gt PrimaryKey 1324 PColumn AUTH lt 1 gt 76 Idefault 1344 PIndex UCS3 gt on 274 324 gt ForeignKey refers to 137 1368 PColumn TITLE lt 2 gt 98 Idefault 389 PTransaction for 3 Auth 4 User 32 Time 23 05 2007 19 14 15 1485 Record
8. Value OrderByClause Y SetFunction Cardinality Collect Element Fusion Intersect Set Collect COLLECT DISTINCT ALL Value FuncOpt Fusion FUSION DISTINCT ALL Value FuncOpt Intersect INTERSECTION DISTINCT ALL Value FuncOpt Cardinality CARDINALITY Value Element ELEMENT Value Set SET Value Typecast CAST XMLCAST Value AS Type TREAT Value AS Sub Type Y A6 9 Statements Assignment SET Target Value Target Value 196 The Pyrrho Book May 2015 SET Target Target Value For a simple assignment of form Target Value the keyword SET can be omitted Target id id Targets which directly contain parameter lists are not supported in the SQL2011 standard Call CALL Procedure_id Value Value Y MethodCall Inside a procedure declaration the CALL keyword can be omitted CaseStatement CASE Value WHEN Values THEN Statements ELSE Statements JEND CASE CASE WHEN SearchCondition THEN Statements ELSE Statements END CASE There must be at least one WHEN in the forms shown above Close CLOSE id CompoundStatement Label BEGIN XMLDec Statements END XMLDec DECLARE Namespace Declaration DECLARE id id Type DECLARE id CURSOR FOR Cu
9. Apart from the owner privilege which can be held by just one user granting privileges directly to users is deprecated It is recommended to grant roles to users instead Similarly attempting to create a hierarchy of roles is also deprecated and in Pyrrho the grant of role A to role B has the effect only of granting role A to all users authorised to use role B at the time of the grant it does not create a permanent relationship between the roles revoking a role from a role does nothing and all roles are in the root namespace This behaviour appears to be a departure from SQL2011 Similarly a grant of privileges does not create any permanent relationship between roles For example granting Select on a Table implies granting select on all of the current columns The grant can be repeated later if new columns are added or the new columns can be granted Similarly in Pyrrho access to a column can be revoked even though the role was previously granted access to the whole table Granting a role to a user is different it means that the user is entitled to exercise the role and any privileges that the role has at the time of use 6 9 Verifying privileges The DBMS should provide one or more system tables to verify the current permissions on an object In Pyrrho this is done by the RoleSPrivilege table Here is an example 58 The Pyrrho Book May 2015 Tables AUTHOR iDelete References GrantDelete GrantReferenc les Libra
10. E internal class MyItem public int val public string str public MyItem int v string s val v str FirstName public override string ToString F return str E private void comboBox1_SelectedValueChanged objec var it comboBox1 SelectedItem as MyItem MessageBox Show it val ToString A1 3 Using SqlServerCe with basic ADO NET The above example used fancy classes such as data adapters and so did the MySQL example These classes have been added to the frameworks to assist with DataGridView a rather complex beast With Windows Presentation Framework ASP NET and mobile platforms we tend to use simpler classes as in this example For fun let s use WPF which does not have DataGridView Create a WPF project and add a local database to it as before If you right click the database in the server explorer and select Properties you will see that the Connection String is something like Data Source C Temp clubWPF Database1 sdf In the Toolbox you will see a DataGrid but just for fun let s work with Grid instead There is a Grid on the design surface Click in the top edge of the Grid to make some columns Select the Events tab in the properties window and double click Loaded Look to see what has happened to the XAML Find the Grid and set its Name members Add using System Data and using System Data SqkServerCe at the top of the code file and declare fields for the co
11. Pel Pho HIL Eke a 13 Dalsia If you are using the PyrrhoSQL client shown give the Database name as Library and click Connect If you are using an ordinary command prompt give the command pyrrhocmd Library We begin by controlling access to the database and then start to build a simple database of books and authors revoke Library from public create table author id int primary key name char not null create table book id int primary key title char not null aid int references author insert into author values 1 Dickens 2 Conrad insert into book values 10 Lord Jim 2 11 Nicholas Nickleby 1 table book Commr Hos kesho Agr H11 Dit Uy gt Coast Fogle enna hehe miho ad ot peyote h ot ee enna hehe beech mi prerary bye cee rot euler ol mer bria author veda 11 Debon 1 11 Coed meri do bock sober iI Deed Jen ELL Hiha Hridi hablo bon 10 Lord iwa a Li Mood Help 2 61 The Pyrrho Book May 2015 This looks okay to a database specialist but the Librarian is not impressed He wants the author s name in the book table after feebly trying to explain about joins provide a special generated column in this table using the standard SQL2008 syntax alter table book add aname char generated always as select name from author a where a id aid Pe Prhe SACL Cc Conair Sa MI Cubre Liny r eee Fade se Cabe ao al ra pe er e AA e rs O A A lal taii ecw This pleases him a bit b
12. ooooononococionacinonanononanononacoonnnnnonnnnnonacnnonanos 165 AS OLA delete the PIO A A A ti 168 AS A O 169 ADE A a A A ia BOYS 171 PO Sep a is eee eee A seca el Nei 180 Appendix 6 Pyrrho SQL SyMtax iscscsecsccsccoscssysonressscecesssncesnesencestssovsencnonsnassoaeetoesosenonassees 181 A61 Statements E A iaat 181 AG Data Derm ofi susiosimi e e E aa 182 AGS ACCESS Control asian id ii S 187 ACA PD ls EE E 188 A0 5 Data Manipulation ainia ire 189 PS aise chen caehaceanesa a a Suma ea manne teach Maney a aS 191 IND ts sdesaaesdeaededssusscaescseguatassbea cvandedarasepoanmanvtenes 193 AGS SOL FUCSIA dde 194 A69 MAMAS a scatennsisoanceneds etanvaec sue E SaS 196 The Pyrrho Book May 2015 AX ML SuppOll taccu2e hese A aids hee A ee nee Bee 198 Appendix 7 Pyrrho s condition codes esssesssoessoossooesssesssesssoossoosssoessoeessesssoosssossssssssesssose 200 Appendix 8 Pyrrho s System Tables e ssesssocssoossoossssesssesssoossoossssesssesssesssoosesossssssssesssose 204 Appendix 9 The Pyrrho Class Library Reference cccsscssssssccsscssscsscsssscssscssoesooss 206 A9 1 DatabaseBaror tinta mane 207 A92 Dt doo 207 E PyrhoATray ooreen eE E RREA ARS E TE EE EE Rh 207 POA o e a E E E dara AS 207 ADS PyrrhoCommand ni R T ai 207 ADO PYME ri 208 AGF PyreHODOCUMENE ices neina ica 209 A IA TO 209 AS9 O PyrrhoR cadera tanda lia ibi 209 A9 LO P yoo Wade 210 ASAT Pyrrho Table a 210 A A de
13. AlterDomain SET DEFAULT Default DROP DEFAULT TYPE Type AlterCheck AlterBody AlterOp AlterOp AlterOp TO id Statement ADD DROP Metadata Default Literal DateTimeFunction CURRENT_USER CURRENT_ROLE NULL ARRAY MULTISET AlterCheck ADD CheckConstraint ADD DROP Metadata DROP CONSTRAINT id Note that anonymous constraints can be dropped by finding the system generated id in the SysSTableCheck SysSColumnCheck or SyssDomainCheck table see section 8 1 CheckConstraint CONSTRAINT id CHECK XMLOption SearchCondition XMLOption WITH XMLNAMESPACES XMLNDec XMLNDec Y XMLNDec string AS id DEFAULT string NO DEFAULT The following standard namespaces and prefixes are predefined http www w3 org 1999 02 22 rdf syntax ns AS rdf hnttp www w3 org 2000 01 rdf schema AS rdfs http www w3 org 2001 XMLSchema AS xsd http www w3 org 2002 07 owlt AS owl AlterTable TO id ADD ColumnDefinition ALTER COLUMN id AlterColumn DROP COLUMN id DropAction ADD DROP TableConstraintDef VersioningClause ADD TablePeriodDefinition AddPeriodColumnList ALTER PERIOD id TO id DROP TablePeriodDefinition AlterCheck ADD DROP Metadata AlterColumn TO id POSITION int 183 The Pyrrho Book May 2015 SET DROP NOT NULL ColumnConstraint AlterDomain Ge
14. Grant can only be used in single database connections section 3 4 For roles see section 5 5 Revoke REVOKE GRANT OPTION FOR Privileges FROM GranteeList REVOKE ADMIN OPTION FOR Role_id Role_id FROM GranteeList Revoke can only be used in single database connections Revoke withdraws the specified privileges in a cascade irrespective of the origin of any privileges held by the affected grantees this is a change to SQL2011 behaviour See also sections 5 5 and 7 13 Privileges ObjectPrivileges ON ObjectName ObjectPrivileges ALL PRIVILEGES Action Action Action SELECT id 4 id Y DELETE INSERT id 4 id UPDATE id id REFERENCES id id USAGE TRIGGER EXECUTE OWNER The owner privilege Pyrrho specific can only be granted by the owner of the object or the database and results in a transfer of ownership of that object to a single user or role not PUBLIC Ownership always implies grant option for the owner privilege References here can be to columns methods fields or properties depending on the type of object referenced by the objectname ObjectName TABLE id DOMAIN id TYPE id Routine VIEW id 187 The Pyrrho Book May 2015 DATABASE The Pyrrho specific OWNER Privilege is the only grantable privilege on the Pyrrho specific DATABASE ObjectName and results in a transfer of
15. The Pyrrho Book May 2015 This example could be extended by considering the actual use made of the Played table in calculating the current rankings etc A3 2 A forensic investigation Examine the log of the club database as described in the lecture Look at the last few transactions What are the user and role Try writing select statements in the manner described in the lecture to find the previous values of things that have been changed Also look at the current RoleSPrivilege table A3 3 Some more PyrrhoDB stuff will be updating the OSPnn iso files every so often so always use the most recent highest numbered Use this to overwrite the folder you have previously installed on your virtual machine and then you will be able to use the new binaries while retaining any databases you have developed When Pyrrho starts up it gives the date of the server There is a manual in the distribution on your virtual machine and from the PyrrhoDB website http pyrrhodb com A lot of the same material is available in the Sample code section of the website including full reference details for the SQL that Pyrrho uses There is also the blog which is accessible from the website Here are a few pointers that you might find useful in your coursework 1 You can use the pyrrhodb command line to import data from a text file You first need to create a table with suitable columns to receive the data The latest version of the manual says
16. ins he he P Box Me a me ne bs eee tun wwe 2 0 encoding UTS T gt lt ruel gt ron gt Tie Micholas Nickelhy lt T re gt lt row gt ENT Titles Great Expectations Tri cinay lt roat gt The relationship of this Library database to the one in the section 7 1 is approximately as follows In role Library 72 The Pyrrho Book May 2015 Create role Web Grant select on author to Web Grant select on book to Web Insert into book title aid values Great Expectations 1 In role Web Alter table author entity Alter table author alter id attribute 7 4 Data Visualisation and CSS The system table RoleSObject shows the metadata defined for database objects Some of these are for control of Pyrrho s Web services In particular Pyrrho offers some simple charts that can be obtained via the Web services The Metadata flags and the string constraint are Pyrrho extensions Attribute and Entity affect XML output in the role Histogram Legend Line Points Pie for table view or function metadata Caption X and Y for column or subobject metadata affect HTML output in the role HTML responses will have JavaScript added to draw the data visualisations specified The string is for a description and for X and Y columns is used to label the axes of charts If the table s description string begins with a lt it will be included in the HTML so that it can supply CSS st
17. oer eae 5 _Client 4 221 _Database 7 475 _Partition 14 Name PartitionServer PartitionServerConfigUser PartitionServerConfigPassword Base BaseServer sePassword Table SegmentName Column MinValue MaxValue IncludeMin IncludeMax 127 0 0 1 5435 Student 13 Don t worry about asusrog here it s just the name of the PC am using The ServerRole 15 contains the bits 7 that we saw in a previous tutorial together with 8 indicating BaselsRemote The entry does not give the name of the base database this is actually written at the start of the binary partition file as can be seen in the LogS for D2 shown on the previous page But on both servers as in the previous tutorial the servers show the same list in the _Database and _Partition table by collecting data from other servers in the lists 167 The Pyrrho Book May 2015 On A delete the single partition recordin_ PyrrhoCmd p 5434 _ delete from _Partition SQL gt C E OSP gt PyrrhoCmd p 5434 _ SQL gt Delete from _Partition 1 records affected SQL gt C E OSP gt m 6 Verify that E still shows the correct contents on both servers but the logfile or Sys Table for D2 shows that the records in this partition have been deleted SysSTable for D on A shows 4 rows in E and SysSTable for D2 on B shows 0 rows in E Partitions that are no longer in use are not actually deleted from the file system as the transaction logs should re
18. A9 11 PyrrhoTable A PyrrhoTable is constructed internally by every invocation of ExecuteReader As in ADO NET DataTable there are properties called Rows and Columns and an array of PrimaryKey columns There is a strongly typed subclass PyrrhoTable lt T gt which has a public property Instances of type Dictionary lt IComparable object gt For tables with a simple primarykey this dictionary can be used to find a single entity of type T These correspond one to one with the Rows but updates are not synchronised with the database A9 12 PyrrhoTransaction This class imitates IDbTransaction Method or Property Explanation void Commit Commit the transaction bool Conflict Gets whether a conflicting transaction has been committed since the start of this transaction Requires a round trip to the transaction master server If Conflict is true a subsequent Commit will fail but the transaction is not closed void Rollback Roll back the transaction 210 The Pyrrho Book May 2015 Appendix 10 Pyrrho s Connection String Pyrrho allows multi database connections with some limitations see section 2 8 3 More than one database on the same server can be specified using a comma separated list of Files but two mechanisms are provided for more complex scenarios In Android and embedded editions of Pyrrho the Host and Port fields are not provided but remote hosts and ports can be specified for a database using
19. Between 193 BinaryOp 192 BooleanExpr 193 BooleanFactor 193 BooleanTerm 193 BooleanTest 193 Call 197 Cardinality 196 CaseStatement 197 Ceiling 194 CharacterType 188 CheckConstraint 183 Close 197 Coalesce 194 Collate 188 Collect 196 ColRef 186 Cols 186 ColumnConstraint 185 ColumnConstraintDef 185 ColumnDefinition 185 ColumnOption 186 ColumnOptionsPart 186 ColumnRef 192 Comparison 193 CompOp 193 CompoundStatement 197 CondInfo 197 Condition 197 ConditionCode 197 ConditionList 197 Contains 193 Correlation 194 Count 194 Covariance 195 Create 184 CursorSpecification 189 213 DatabaseError 206 Date 207 DateTimeField 193 DateTimeFunction 196 DateTimeType 189 Declaration 197 Default 183 DefinedType 189 DeletePositioned 189 DeleteSearched 189 DomainDefinition 185 DropAction 187 DropObject 187 DropStatement 187 Element 196 EndField 193 Event 186 Every 193 Exclusion 190 Exists 193 Exponential 195 Extract 195 ExtractField 195 Fetch 198 FetchFirstClause 191 Files 211 FloatType 188 Floor 195 Fold 196 ForStatement 198 FromClause 190 FuncOpt 194 FunctionCall 194 Fusion 196 GenerationRule 185 GetDiagnostics 197 GetFileNames 208 Grant 187 Grantee 188 GranteeList 188 GroupByClause 190 Grouping 195 GroupingSet 190 GroupingSpec 190 HandlerType 197 HavingClause 190 Host 211 How 198 HttpRest 182 IfStatement 19
20. IndexDone e Data Reader for t The Pyrrho Book May 2015 And onA PyrrhoCmd p 5434 D table E Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EX Command Prompt OSP T p 5435 d B s 0 S 0 M 0 onnection 18 Coordinator 127 0 0 1 5435 Files D Role User guest 18 Protocol byte RemoteBegin connection 20 Coordinator 127 8 0 1 5435 Files D Role User guest 20 Protocol byte RemoteBegin 20 Protocol byte IndexLookup 20 Protocol byte IndexLookup 20 Protocol byte IndexNext 20 Protocol byte IndexNext connection 22 Files D User asusrog Student 22 Protocol byte ExecuteReader Connecting D2 27 127 0 0 1 5435 14 Protocol byte IndexLookup 14 Protocol byte IndexNext 14 Protocol byte IndexNext About to Begin D2 27 Enter to Continue ndexNext returns IndexData 22 Protocol byte Data IIndexNext returns IndexDone 22 Protocol byte Data rdinati i for tid 10 22 Protocol byte CloseReader 22 Coordinating Commit for tid 14 LocalTransaction D h E Enter to st nection 17 Coordinator 127 0 0 1 5 LocalSlave D2 Phase 1 for D 24 Enter to start Phase 1 for D2 25 Enter to start About to Close D2 27 Enter to Continue losed D2 27 Enter to Continue Phase 3 for D 24 Enter to start Phase 3 for D2 25 Enter to start Phase 4 for D 24 Enter to start Phase 4 for D2 25 Enter to start 22 tid 14 Committed H DATA E gt A pa x
21. Methods defined for user defined types RoleSObject Metadata for database objects RoleSParameter Parameter information for user defined methods and procedures RoleSPrimaryKey Primary key information for base tables RoleSPrivilege Access privileges that have been granted on database objects RoleSProcedure User defined Procedures RoleSSubobject Metadata for database subobjects e g view columns RoleSTable Base tables in the current database RoleSTableCheck Table check constraints RoleSTablePeriod User defined periods RoleSTrigger User defined triggers RoleSTriggerUpdateColumn Column update information specified for user defined triggers RoleSType User defined types RoleSView User defined Views Logs The transaction log a readable synopsis of each entry in the log LogSAlter Details for ALTER records in the log see also CHANGE EDIT MODIFY LogSChange Details for CHANGE records in the log LogSCheck Details for user defined check conditions LogSColumn Details for column definitions 204 The Pyrrho Book May 2015 LogSConflicts Details of conflicting log entries for each log entry LogSDateType Details for user defined date types LogS Delete Details for DELETE records in the log LogSDomain Details for DOMAINS specified in this database LogSDrop Details for DROP
22. 100 WHER UPDATE Accounts SET balance balance 100 WHER acctID 101 acctID 202 E El E T SELECT FROM Accounts ROLLBACK Experiment 2 Transaction logic following commands are sensitive to previous balance values BEGIN TRANSACTION UPDATE Accounts SET balance balance 2000 WHERE acctID 101 I think you should do something else just here UPDATE Accounts SET balance balance 2000 WHERE acctID COMMIT SELECT FROM Accounts Do we have a problem 202 Experiment 2b Transaction logic restoring the original contents BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES 101 1000 INSERT INTO Accounts acctID balance VALUES 202 2000 SELECT FROM Accounts COMMIT Advanced topic Experiment with IF structure See the Stored Procedure at the end of this file i a a aa a end of the Advanced topic ssss Ss sess 4555 110 The Pyrrho Book May 2015 A1 3 Experimenting with Concurrent Transactions For concurrency experiments we will open two parallel sessions Note SERIALIZABLE is the default and only supported isolation level in Pyrrho So some of our test cases are E not relevalnt in Pyrrho To start with fresh contents we enter follo
23. 154 The Pyrrho Book May 2015 E Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d B p 5435 s 0 S_ E Command Prompt OSP T d C p 5436 s 0 S 0 M 0 10 Protocol byte CloseConnection Connecting D 9 127 0 0 1 5435 Exception 00000 About to Begin D 9 Enter to Continue _ 49 Rollback 5 Protocol byte Data 5 Filabout to Close D 13 Enter to Continue 5 Protocol byte Data Closed D 13 Enter to Continue 5 Protocol byte CloseReader 16 Ends with 9 5 Coordinating Commit for tid 3 Connection 12 Coordinator 127 0 0 1 5436 RemoteTransaction D Connecting D 15 127 0 0 1 5434 Phase 1 for D 10 Enter to start About to Begin D 15 Enter to Continue About to Close D 9 Enter to Continue 12 Protocol byte RemoteBegin Closed D 9 Enter to Continue 12 Protocol byte CloseConnection Phase 3 for D 10 Enter to start F i Phase 4 for D 10 Enter to start Connecting D 9 127 0 0 1 5435 About to Close D 15 Enter to Continue About to Begin D 9 Enter to Continue Closed D 15 Enter to Continue Closed D 9 Enter to Continue 12 Ends with 9 5 tid 3 Committed Connection 14 Coordinator 127 0 0 1 5436 5 Protocol byte ExecuteReader Connecting D 17 127 0 0 1 5434 Connecting D 9 127 0 0 1 5435 About to Begin D 17 Enter to Continue EM Command Prompt PyrrhoCmd p 5436 D e T DATA E A Name L osp L D osp into E va
24. 22007 22008 22009 2200D 22006 2200 2200K 2200N 2200S 22010 22011 22012 22013 22014 22015 22018 22019 2201B 2201M 22021 22022 22023 22024 22025 22101 22102 22103 22104 22105 22106 22107 22108 22201 22202 22203 22204 22205 22206 22207 22208 200 Message Template and comments Warning column cannot be mapped Not found Attempt to assign to non updatable column Cardinaility error Element requires a singleton multiset Data and incompatible type error Numeric value out of range Illegal null value Wrong types expected got Expected keyword at Minus sign expected DateTime DateTime format error Invalid escape octet Type mismatch expected got at Nonidentical notations with the same name Nonidentical unparsed entities with the same name Invalid XML content Invalid XML comment Invalid indicator parameter value Substring error Divide by zero Invalid preceding or following size in window function Year out of range Interval field overflow Invalid character value for cast Invalid escape character Invalid regular expression Namespace not defined Illegal character for this char set Bad document format Too few arguments Too many arguments Type expected Bad row compare Type mismatch on concatenate Multiset element not found Incompatible multisets for union Incompatible multisets for intersection Incompatible multisets for except Exponent expected Type
25. A s 0 5 0 M 0 2 Protocol byte Fetch StartCommit for osp at 34 T p 5434 d A s 5 0 M Enter to siconnection 4 Coordinator 127 0 0 1 5436 F pbStorage Flush complete for C _ osp len 979 Pyrrho DBMS c 2015 Malcolm Crowe and Uni 4 Protocol byte RemoteBegin Phase 4 for _ 4 Enter to start 5 2 19 March 2015 w pyrrhodb com Protocol byte IndexLookup 3 tid 2 Committed PyrrhoDBMS protocol on 127 0 0 1 5434 Protocol byte IndexNext Connecting 5 127 0 0 1 5435 atabase folder MAN Protocol byte IndexLookup About to Begin D 5 Enter to Continue Protocol byte IndexNext Connecting _0127 0 0 1 5435 6 127 0 0 1 5435 2 Protocol byte RemoteBegin Protocol byte CloseConnecti About to Begin 0 0 35 6 Enter to Continue 2 Protocol byte CloseConnection Exception 90000 1 Coordinating Commit for ti Exception 00000 2 Rollback Reconfigure 2 Rollback About to Close D 5 Enter to Continue RemoteTransaction D 2 Ends with 9 Closed D 5 Enter to Continue ProxyTransaction _ 127 0 0 1 5435 Connection 4 Coordinator 127 0 0 1 5435 Fil 2 Ends with 9 Phase 1 for _ 5 Enter to start 4 Protocol byte RemoteBegin 4 Protocol byte Prepare Phase 1 for D 7 Enter to start 4 Protocol byte CloseConnection Prepare 1 physicals About to Close D 5 Enter to Continue Exception 00000 Record Closed D 5 Enter to Continue 4 Rollback Prepare rdCs Phase 1 for _ 9 Enter to start 4 Ends with 9 Prepare complete About to Prepare _ 127 0 0 1 5435 6 Enter
26. CONSTRAINT id TableConstraintDef TableConstraintDef UNIQUE Cols PRIMARY KEY Cols FOREIGN KEY Cols REFERENCES id Cols USING Values ReferentialAction The Using expression here is an extension to SQL2011 behaviour See section 5 2 2 TablePeriodDefinition PERIOD FOR PeriodName Column_id Column_id Y PeriodName SYSTEM_TIME id TypedTableElement ColumnOptionsPart TableCnstraint ColumnOptionsPart id WITH OPTIONS ColumnOption ColumnOption ColumnOption SCOPE Table_id DEFAULT Value ColumnConstraint Values Value Value Cols ColRef ColRef PERIOD ApplicationTime_id The period syntax here can only be used in a foreign key constraint declaration where both tables have application time period definitions and allows them to be matched up ColRef Column_id Field_id DESC The Field_id syntax is Pyrrho specific and can be used to reference fields of structured types or documents The desc option is for the MongoDB Create Index syntax and is allowed only for document field references ReferentialAction ON DELETE UPDATE CASCADE SET DEFAULT RESTRICT The default ReferentialAction is RESTRICT Constraints are retrospective they cannot be applied if existing data conflicts with them A new default value will be applied to any existing null values but dropping or changing a default
27. DISTINCT Literal int float string TRUE FALSE l X hexit id 4 Domain_id Type_id Namepsace_id id uri DATE date_string TIME time_string TIMESTAMP timestamp_string INTERVAL interval_string IntervalQualifier Strings are enclosed in single quotes Two single quotes in a string represent one single quote Hexits are hexadecimal digits 0 9 A F a f and are used for binary objects 192 The Pyrrho Book May 2015 The syntax with is special in Pyrrho and is added for RDF OWL support e g 2 5 Munits ampere In the RDF OWL syntax in the double quoted part is a special character and introduces a locale Note however that without the 2 5 would be an id and not a string and the lt gt do not normally behave like quotes Dates times and intervals use string single quoted values and are not locale dependent For full details see SQL2011 e g a date has format like DATE yyyy mm dd a time has format like TIME hh mm ss or TIME hh mm ss sss a timestamp is like TIMESTAMP yyyy mm dd hh mm ss ss an interval is like e g INTERVAL yyy YEAR INTERVAL yy mm YEAR TO MONTH INTERVAL m MONTH INTERVAL d hh mm ss DAY 1 TO SECOND INTERVAL sss ss SECOND 3 2 etc IntervalQualifier StartField TO EndField DateTimeField StartField IntervalField int Y EndField IntervalF
28. Ends with 3 x aes p 5 Home Share View E F int E lu E DATA E gt A insert into E values table E Lj osp _ _ 127 0 0 D osp 1 5434 D _ 127 0 0 1 5434 974 127 0 0 1 54 E 1 543 true true Three more Enters and the other transaction is committed and the saved data removed EM Command ie OSP T asi d A s 0 S 0 M 0 rdCs DbStorage Flush Eta ae A D _ 127 1 5434 974 127 0 0 1 543 e complete Phase 2 for D2 15 Enter to start out to Requ D2 13 Enter to Continue 7 Enter to start 435 14 Enter to Cont byte Requ h complete for 1 byte R StartCommit for D p Flush complete for AB with 31 1 byte Re StartCommit for Ey Enter to start About to Commit D2 13 Enter to Continue EM Command Prompt OSP T p 5435 d B s 0 S 0 M 0 len 1163 to Continue Home Share View t I DATA E gt A Osp _ 127 0 0 1 5434 974 _ 127 0 0 1 543 D osp D _ 127 0 0 1 5434 974 _ 127 0 0 1 54 Student 4 items B D2 osp 30 03 2015 22 osp Now A begins to remote its Saved data 176 password The Pyrrho Book May 2015 EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 X 5 dAB s 0 S 0 M 0 Phase 2 for D2 15 Enter to start About to Request D2 13 Enter to Continue Phase 2 for _ 17 Enter to start About to Request _ 127 0 0 1 5435 14 Enter to Continu
29. For now let s just consider GET actions As we will see in the next posting one simple way of handling moderate security for PUT DELETE and POST is to grant Insert Update and Delete to a role with a hard to guess name We can use REST to explore the Web role of the database For the Author table AUTHOR has been declared as an entity and ID has been declared as an attribute so the output has a different form GF location m eruon er ro T ow lt 1D gt 1 Im Jos Great Expectations lt 311 AID gt 1 lt A1D Author gt Dickens lt Author Avovahle gt Tree lt Avalatie 10 gt 10 lt 30 thes Lord Jim lt bd AID gt 2 lt AlD Author gt Conrad lt A hor gt alabla gt True lt Awailabk row ID gt 28 lt ID Teles Nicholas Mickelby lt 7 tle AID gt i lt AIn r Author gt Dickhens lt Author Avarable gt Tree lt Awalabk oot We can limit the output to particular columns 71 The Pyrrho Book May 2015 s aml verunn 0 encodrg UTF 57 gt croct gt CTION gt lt MAME gt Dickens lt NAME gt E TGN gt lt roat gt We can select rows satisfying a particular set of conditions lt xmi veruon 0 enco ro UTF 57 gt lt rocl gt AUTHOR 10 1 gt lt NANE gt Dickens lt NAME gt AUTHOR gt lt roat gt P Oc am a Pain wares 2 0 ancag UT Oo T gt lt ruet gt lt AUTIOON IDe 2 gt lt WAME gt Conrad SAMEy lt AUTHORs roots
30. Pyrrho automatically creates three tables called Client Database and _Partition inside any new configuration database The first two will feature in this tutorial as the name implies the _Partition table is for configuring partitioned databases Anyway the command succeeds and we get another SQL gt prompt The D osp in Bis a binary copy of the D database from A as this is the effect of the mumbo jumbo in the above insert command But the two configuration databases are different as we will now see 125 The Pyrrho Book May 2015 A4 4 Examining the configuration file At the SQL gt prompt examine the _ database with the commands to the B server table _Database We inserted one record in the _Database table but we see two We did not add anything to the _ Client table but we see a record It is clear that a lot has been happening behind the scenes The details are quite technical and involve distributed transactions there are some explanations given in section 6 of this document You will see a different machine name from asusrog table Sys Table Reassuringly though the SysSTable table shows that the _ database on B really does have just one record the one we inserted The record we inserted called for the creation of binary storage on B or a database from A so the configuration database on A was created to ensure the copy is kept updated by A which of course continues to be the transaction master for the
31. Pyrrho will roll back the transaction For example if a transaction computes a value to insert in the database it should be invalidated by changes to any values used in the computation Pyrrho calls these ReadConstraints Similarly referential constraints called IndexConstraints in the code must also be checked again at Commit time in case another transaction has inserted a record with a conflicting unique key or deleted a record that our transaction intends to refer to For this reason the data used in the Commit process consists of the list of proposed Physicals together with sets of ReadConstraints and IndexConstraints For a remote database It is this collection of data and not the final binary data that must be sent to the remote master server for processing Unfortunately we are left with the situation that serialisation must ultimately be decided by a single transaction master server The most we can use the cloud for in transaction management is as an enterprise system bus routing transaction streams to the transaction master To ensure that we have read the most up to date version we simply call commit if it is not up to date our transaction will fail and re running the query will get its new value 88 The Pyrrho Book May 2015 Chapter 10 Partitioned Databases Classically there are two sort of partitioning for relational databases so called vertical partitioning where a relational table has some columns provided b
32. Role Based Security seesseessocesooesooesssecssccesocesocssoocesocsssecesocesoossoosessesssecesocssooses 53 A 53 6 1 Application or DBMS based security iii dese eendngeuses 54 6 2 Forensic investigation of a database seso 54 SPT VIS TESA e Zotar A E E sda acl ste E A E E E 57 GE EEO A E E E E E E N A A 57 6 7 Lhe role tara A ds 57 6 5 Revoking privileges tanne eds 58 6 9 Ventana pri vilet S O EG TE G 58 Chapter 7 Role based modelling and legacy data ooocmom 60 AMEX PE Ged gies tava esgeri e e a r s a a sateet ge 60 7 1 How the mechanism Works viii ii obedeci 65 T2 Legacy ALA ss cepeu crete params teams n e a a a e E E E a Satuntdaan 69 Ta The REST Servi nemenr a is 69 The Pyrrho Book May 2015 Data VASU ALES a On and CS St A ie 73 Chapter 8 Web semantics and OWL ccissssecissesssacssssonnsssscsssossecesesiveooassvosenuscosesntievennavsesoaes 74 SC MIR TS first Step A E E AEE E E E ne ase Ua 74 Roe O AA D BA o sci ee nae dain ace EE E ucts esse ans E ecsateaens 75 8 3 IR referencesand SU A O 76 8 4 Row and table subtypes 225 aii 76 8 9 Provena 2 sh AA A ds Sa ea Sta 71 OREA MIAE AO TINET A NE 17 A a a aa Tee a eae aose i 11 Intervalo E A AE E A ieee das iaa 78 Localisation and COM AMONG a A 78 8 7 Usine str ctured LY PES di A eee ah eee deere ones 79 8 8 Stored Procedures and MICU OAS i 3 55 cae eii 80 8 9 Condition handling Statements iis 2 8 tet oodl bet A A tes 81 RATIO LE Seca ok nc AEE EE I
33. See section 5 2 1 DomainDefinition StandardType UriType DEFAULT Default CheckConstraint Collate Ordering RELATIVE MAP WITH Routine STATE TableContents TableClause TableClause Y VerisoningClause OF Type_id TypedTableElement TypedTableElement AS Subquery VersioningClause WITH SYSTEM APPLICATION VERSIONING WITH APPLICATION VERSIONING is Pyrrho specific see section 5 2 3 TableClause ColumnDefinition Metadata TableConstraint TablePeriodDefinition ColumnDefinition id Type DEFAULT Default ColumnConstraint CheckConstraint Collate id GenerationRule id Table_id Column_id The last version is a convenience form for lookup tables e g if a b has domain int then a b is a shorthand for int check value in select b from a GenerationRule GENERATED ALWAYS AS Value UPDATE Assignments Y GENERATED ALWAYS AS ROW START END The update option here is an innovation in Pyrrho ColumnConstraint CONSTRAINT id ColumnConstraintDef ColumnConstraintDef NOT NULL PRIMARY KEY REFERENCES id Cols USING Values ReferentialAction UNIQUE DEFAULT Value GenerationRule The Using expression here is an extension to SQL2011 behaviour See section 5 2 2 A column default value overrides a domain default value 185 The Pyrrho Book May 2015 TableConstraint
34. Student _ osp LJ D osp Ei iB Xx Home Share View t E DATA E gt B ame tie y E d p 5434 D L_ D2 osp 30 03 2015 22 osp 30 03 2015 22 20 Notice the interaction between the servers when we do almost anything as a minimum the partitions check that the base server is not trying to do further partitioning and obviously collecting the data for table E needs cooperation of both servers You can continue the tutorial to the next phases where we add further records and delete the partition segment Quite a few more applications of the Enter key are required 180 The Pyrrho Book May 2015 Appendix 6 Pyrrho SQL Syntax A clickable HTML version of these details is available at www pyrrhodb com In this section capital letters indicate key words many of these words are reserved words see the website for a list of reserved words Tokens such as id int string are shown as all lower case words Mixed case is used for grammar symbols defined in the following productions The characters are part of the production syntax Characters that appear in the input are enclosed in single quotes thus Where an identifier representing an object name is required and the type of object is not obvious from the context locutions such as Role_id are used There are three tokens xmlIname iri and xml which are used in XPath below which are extensions to SQL2011 These tokens are not enclo
35. Wild The data type of a wildcard for traversing compound indexes Bool The Boolean data type see BooleanType RdfBool The iri defined version of this Blob The data type for byte MTree Multi level index used in implementation of MTree indexes Partial Partially ordered set ditto Char The unbounded Unicode character string RdfString The iri defined version of this XML The SQL XML type Int A high precision integer up to 2048 bits Rdflnteger The iri defined version of this in principle unbounded Rdfint value gt 2147483648 and value lt 2147483647 RdfLong value gt 9223372036854775808 and value lt 9223372036854775807 RdfShort value gt 32768 and value lt 32768 RdfByte value gt 128 and value lt 127 RdfUnsignedint value gt 0 and value lt 4294967295 RdfUnsignedLong value gt 0 and value lt 18446744073709551615 RdfUnsignedShort value gt 0 and value lt 65535 RdfUnsignedByte value gt 0 and value lt 255 RdfNonPositivelnteger value lt 0 RdfNegativelnteger value lt 0 RdfPositivelnteger value gt 0 RdfNonNegativelnteger value gt 0 Numeric The SQL fixed point datatype RdfDecimal The iri defined version of this Real The SQL approximate precision datatype RdfDouble The iri defined version of this RdfFloat Defined as Real with 6 digits of precision Date The SQL date type RdfDate The iri defined version of this Timespan The SQL time type Timestamp The S
36. are not currently used because they don t quite match the company s needs The database data files are accessed by the database server so they normally belong to the user account that starts up the database server often this is a special anonymous account The database server controls who can connect to the database The Pyrrho database management system is named after an ancient Greek philosopher Pyrrho of Elis 360 272BC who founded the school of Scepticism We know of this school from writers such as Diogenes Laertius and Sextus Empiricus and several books about Pyrrhonism e g by Floridi have recently appeared And their philosophy was called investigatory from their investigating or seeking the truth on all sides Diogenes Laertius p 405 Pyrrho s approach was to support investigation rather than mere acceptance of dogmatic or oracular utterance Accordingly in this database management system care is taken to preserve any supporting evidence for data that can be gathered automatically such as the record of who entered the data when and if 14 The Pyrrho Book May 2015 possible why and to maintain a complete record of subsequent alterations to the data on the same basis The fact and circumstances of such data entry and maintenance provide some evidence for the truthfulness of the data and conversely makes any unusual activity or data easier to investigate This additional information is available normally
37. as defined in section 7 5 above Thus window functions cannot be used within expressions or as function arguments In Value NOT IN Table _Subquery Value Value Y Like Value NOT LIKE Value ESCAPE Value Like_Regex Value NOT LIKE_REGEX Pattern_Value FLAG Value Member Value NOT MEMBER OF Value Null Value IS NOT NULL Of Value IS NOT OF ONLY Type ONLY Type CONTENT DOCUMENT VALID Similar Value NOT SIMILAR TO Regex_Value ESCAPE char The Regex_Value is an expression whose value is a character string that parses recursively as follows RE RT RT RT RF RF RF RP Y unsigned unsigned Y RP RC RR RR RR unsigned RE RR RC char char id Y RC char Vchar Some SOME DISTINCT ALL Value FuncOpt Unique UNIQUE Table Subquery PeriodBinary PeriodPredicand OVERLAPS EQUALS IMMEDIATELY PRECEDES SUCCEEDS PeriodPredicand See also Contains above PreiodPredicand id id PERIOD Value Value A6 8 SQL Functions FunctionCall NumericValueFunction StringValueFunction DateTimeFunction SetFunctions TypeCast XMLFunction UserFunctionCall MethodCall NumericValueFunction AbsoluteValue Avg Ceiling Coalesce Correlation Count Covari
38. ex Message 2 pect Table check ACCOUNTS SUFFICIENTEUNDS fails for table i Cancel For reasons of space the UI code is omitted here Examination of the code above is for most purposes a sufficient introduction to the ADO NET API The only aspect that is not obvious is that you can only have one DataReader open per connection this is an ADO NET restriction If you have a single connection and you open a DataReader with rdr cmd ExecuteReader then you must call rdr Close before you open another reader You can have several connections open but in that case you are not guaranteed that they will see exactly the same data as they have started at different times 3 4 The Java Library The Pyrrho Java Connector OSPJC and the org pyrrhodb package have been significantly modified as of April 2015 In earlier versions of Pyrrho there was an attempt to allow client applications to define the data model unilaterally using Java annotations in the manner specified for javax org From around version 4 5 this has really been untenable and annotations that differ from the database s implied data model will in future be reported as errors The library is contained in OSPJC bin in the Open Source Distribution of Pyrrho It is best to copy this folder to where your Java project is and compile and execute with javac cp XXXX jJava java cp XXXX Some features of JDBC 4 1 are completely incompatible with the architecture of PyrrhoDB
39. it offers more fine grained behaviour than rollback as it merely removes any changes made in the scope of the handler SIGNAL condition setlist Here the options for condition are SQLSTATE string or any identifier The setlist allows a set of keywords defined n the SQL standard corresponding to items in the diagnostics area For example you can pass a reason in the diagnostic area using the MESSAGE_TEXT keyword Examples The following functions perform the same task The first uses a handler while the second uses a for statement create function gatherl returns char begin declare c cursor for select a2 from a declare done Boolean default false declare continue handler for sqlstate 02000 set done true declare a char default declare p char open c repeat fetch c into p if not done then if a then set a p else set a a p end if end if until done end repeat close c return a 81 The Pyrrho Book May 2015 end create function gather2 returns char begin declare b char default for select a2 from a do if b then set b a2 else set b b a2 end if end for return b end dl Shortcut to PyrrhoCmd exe L gt insert into c valuesCgather2 gt gt L gt table c 82 The Pyrrho Book May 2015 Chapter 9 Distributed Databases For reasons of availability security governance and purpose it is often useful to consider distribute
40. saved as or if available loaded from an XML document with name name xml Thus a database administrator can carefully take a database offline by throttling and then turning off profiling to record a snapshot before shutting down a server and in this way a full profile of normal operations 49 The Pyrrho Book May 2015 can be maintained This level of completeness for profile information will not be achieved if the database server is simply killed If profiling is enabled any failed transaction will report its profile The system profile table will contain the number of successful and failed transactions recorded for this profile the number of successful transactions will be based on the entire history of the database while the number of failed transactions recorded will be based on the available information from recorded periods of full profiling or since the time profiling was enabled for the server If profiling is turned on a set of system tables Profiles ProfileSReadConstraint ProfileSRecord ProfileSRecordColumn and ProfileSTable enable inspection of the real time state of the profile information always excluding any information about transactions in progress As with other system tables these tables are not persisted but instrument the running server by exposing in memory data structures as if they were database tables The profile viewer described in section 5 8 obtains profile information from these tables or from the XML docu
41. section A3 3 Data is retrieved from the database using TABLE or SELECT statements as indicated above If data returned from the server includes blobs by default PyrrhoCmd puts these into client side files with new names of form Blobnn Blobs retrieved to the client side by this method end up in PyrrhoCmd s working directory which is usually different from the database folder To view them it is usually necessary to change the file extension e g to Blob1 gif However on the server side such data is actually stored permanently inside database files Transactions in Pyrrho are mandatory and are always serializable By default each command is committed immediately unless an error occurs Alternatively you can start an explicit transaction at the SQL gt prompt SQL gt begin transaction Then the command line prompt changes to SQL T gt to remind you that a transaction is in progress This will continue until you issue a rollback or commit command at the SQL T gt prompt If an error 12 The Pyrrho Book May 2015 is reported by the database engine during an explicit transaction you will get an additional message saying that the transaction has been rolled back Note that this reminder and warning behaviour is generated in the command line client on the basis of naive text matching of begin transaction etc The use of comments and other noise may affect these feedback mechanisms The database engine however is not
42. w pyrrhodb com Connection 2 Coordinator 127 0 0 1 543 PyrrhoDBMS protocol on 127 0 0 1 5434 Connecting D 5 127 0 0 1 5434 DbStorage Flush complete for osp len 979 Database folder A About to Begin D 5 Enter to Continue Phase 4 for 4 Enter to start Connection 2 Coordinator 127 0 0 1 5435 Files 2 Protocol byte RemoteBegin 3 ti Committed 2 Protocol byte RemoteBegin 2 Protocol byte Fetch Connecting D 5 127 0 0 1 5435 2 Protocol byte CloseConnection 2 Protocol byte Fetch About to Begin D 5 Enter to Continue Exception 00000 Connection 4 Coordinator 127 0 0 1 543 Connecting _ Y 435 6 127 0 0 1 5435 2 Rollback Protocol byte RemoteBegin About to Begin 0 0 435 6 Enter to 2 Ends with 9 Protocol byte IndexLookup 1 Coordinating Commit for tid 1 Connection 4 Coordinator 127 0 0 1 5435 File Protocol byte IndexNext Reconfigure 4 Protocol byte RemoteBegin Protocol byte IndexLookup RemoteTransaction D Protocol byte IndexNext ProxyTransaction _ 127 0 0 Protocol byte CloseConnection Phase 1 for _ 5 Enter to start Exception 00000 Phase 1 for D 7 Enter to start 2 Rollback A About to Close D 5 Enter to Continue About to Close D 5 Enter to Continue lc10sed D 5 Enter to Continue Phase 1 5 for _ 4 Enter to start Phase 2 for _ 4 Enter to start Phase 3 for _ 4 Enter to start StartCommit for _ osp at 34 Share View 0 IE OSP gt PyrrhoCmd p 5436 _ SQL gt insert into _Database values D 0 1
43. 1 5434 Prepar 16 Protocol byte RemoteBegin About to Begin D 127 0 0 1 5434 11 Enter to Continue Prepa p 16 Protocol byte GetMaster About to Prepare D 127 0 0 1 5434 11 Enter to Continue About to CheckSerialisation D 127 0 0 1 5434 11 Enter to Co x EX Command Prompt PyrrhoCmd p 5436 D Home Share View dei y ee i S t values D 0 0 4 3 1 dent T DATA E A Name osp D osp into E values 8 2 items We see that C has sent its transaction data direct to A Use the Enter key 11 more times to complete the transaction and get the SQL gt prompt This time no temporary transaction files are written This is because only A is recording the details Bis a slave and C has no storage for D E Command Prompt osp T p 5434 d A s 0 S 0 EN Command Prompt OSP T d B p 5435 s 0 S Command Prompt OSP T p 5436 s 0 S 0 M 0 Connecting D 15 127 0 0 1 5434 Prepare sending GetMaster for D About to Begin D 15 Enter to Continue gt Master 12 Protocol byte RemoteBegin in and Connecting D 127 1 5434 11 127 0 0 1 5434 12 Protocol byte CloseConnection to Begin D 127 0 0 1 5434 11 Enter to Continue i to Prepare D 127 0 0 1 5434 11 Enter to Continue to CheckSerialisation D 127 0 0 1 5434 11 Enter to Co About to Close D 15 Enter to Continue 1 5 for D 11 Enter to start Closed D 15 Enter to Continue to CheckSeri
44. 1 5435 6 127 0 75435 2 Protocol byte RemoteBegin Protocol byte CloseConnection About to Begin 27 0 0 1 5435 6 Enter to Continue 2 Protocol byte CloseConnection X i 1 Coordinating Commit for tid 1 Exception 00000 2 Rollback Reconfigure 2 Rollback bout to Close D 5 Enter to Continue RemoteTransaction D 2 Ends with 9 Closed D 5 Enter to Continue ProxyTransaction _ 127 0 0 1 5435 Connection 4 Coordinator 127 0 0 1 5435 Files 2 Ends with 9 Phase 1 for _ 5 Enter to start 4 Protocol byte RemoteBegin 4 Protocol byte Prepare Phase 1 for D 7 Enter to start 4 Protocol byte CloseConnection Prepare 1 physicals About to Close D 5 Enter to Continue Record Closed D 5 Enter to Continue Prepare 0 rdCs Phase 1 for _ 9 Enter to start Prepare complete About to Prepar 127 0 0 1 5435 6 Enter to Continue About to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con EM Command Prompt PyrrhoCmd p 5436_ Share View AE NOSP gt PyrrhoCmd p 5436 _ SQL gt insert into _Database values D 127 0 0 1 5436 2 password 127 0 0 1 5435 student DATA E A passuord We are now in the Prepare phase for the distributed reconfiguration involving changes to the configuration files on B and C Press Enter 3 Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d B p 5435 s 0 S BR Command Prompt OSP T d C p 5436 s 0 S 0 M 0 E OSP gt osp T p 5434 d
45. 202 BEGIN TRANSACTION UPDATE Accounts SET balance balance 100 WHERE acctID 101 UPDATE Accounts SET balance SELECT FROM Accounts 2 Client B starts will this be a Dirty Read First restoring the original contents by client A BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES E S F NSERT INTO Accounts acctID balance VALUES ELECT FROM Accounts COMMIT 1 client A starts BEGIN TRANSACTION Accounts having balance gt 500 euros SELECT FROM Accounts WHERE balance gt 500 2 Client B starts 101 1000 202 2000 202 BEGIN TRANSACTION UPDATE Accounts SET balance balance 400 WHERE acctID 101 UPDATE Accounts SET balance balance 400 WHERE acctID SELECT FROM Accounts COMMIT 3 Client A continues Let s s the results after client B s transaction SELECT FROM Accounts WHERE balance gt 500 COMMIT Experiment 8 Insert Phantom First restoring the original contents by client A BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES INSERT INTO Accounts acctID balance VALUES SELECT FROM Accounts COMMIT 113 101 1000 202 2000 The Pyrrho Book May 2015 1 client A starts BEGI
46. 3 Starting the server The server is normally started from the command line in the same folder as the server binary in the distribution this is in the Pyrrho or OSP folder closest to the root of the distribution The command line syntax is as follows for Open Source Pyrrho the server name is OSP PyrrhoSvr h host p port s port S port M port d path On Linux systems you will need the Mono runtime installed and the command line begins mono PyrrhoSvr exe The h and p arguments are used to set the TCP host name and port number to something other than 127 0 0 1 and 5433 respectively This can be a useful and simple security precaution Note that the host IP address used must match the host name given in connection strings See Appendix 10 The s and S flags modify the ports for the REST service from the defaults of 8180 and 8133 The d flag can be used to specify the server s database folder we will explore the use of this option and some additional flags in the Appendices on Distributed and Partitioned databases when we model the use of multiple servers The Pyrrho Book May 2015 1 4 Database files PyrrhoSvr exe the folder that contains it and all the database files in this folder are normally owned by the same user called the server account in the following notes Note that the database owner is different as described in this section If the server creates a database file on behalf of a c
47. 5436 D Home Share View e 1 DATA E A a Name L _ osp _ D osp lt 2 items ESLI a m S We see the connection to server C SQL gt table E Command Prompt osp T p 5434 d A s 0 S 0 M Command Prompt OSP T d B p 5435 s EN Command Prompt OSP T d C p 5436 s 0 S 0 M 0 4 Protocol byte Request Phase 3 for _ 5 Enter to start DbStorage Flush complete for B _ _ 12 Connecting D 5 127 0 0 1 5435 Connection 6 Coordinator 127 0 0 1 5434abo0ut to Begin D 5 Enter to Continue Connecting D 9 127 0 0 1 5434 P StartCommit for _ osp at 974 About to Begin D 9 Enter to Continue ppstorage Flush complete for C _ osp len 1142 s 6 Protocol byte RemoteBegin Phase 3 for D 7 Enter to start 4 Protocol byte RemoteCommit Phase 3 for _ 9 Enter to start startCommit for _ osp at 1137 About to Commit _ 127 0 0 1 5435 6 Enter to Continue PbStorage Flush complete for B _ OSP Icjosed _ 127 0 0 1 5435 6 Enter to Continue 4 Ends with 31 Phase 4 for _ 5 Enter to start 6 Protocol byte CloseConnection Phase 4 for D 7 Enter to start Closed D 5 Enter to Continue Phase 4 for _ 9 Enter to start About to Close D 9 Enter to Continue 1 tid 1 Committed Closed D 9 Enter to Continue 1 Ends with 1 6 Ends with 9 z Connection 5 Files D User asusrog Student Connection 8 Coordinator 127 0 0 1 543 5 Protocol byte ExecuteReader Connecting D 11 127 0 0 1 5434 Connecting D 5 127 0 0 1 5435 Abou
48. B p 5435 s 0 S 0 M 0 mi x EX Command Prompt osp T p 5434 d A Continue Enter to Continue Continue Enter to Continue _ 127 0 0 1 5434 6 Enter to C r to start DbStorage Flush complete _ _ 127 0 0 1 5434 974 127 0 0 1 5435 974 osp len 105 Phase 2 for 9 y Enter to Continue for _ 5 connecting D 7 12 A in D 7 En OSP gt PyrrhoCm ate tat Share View E DATA E A insert into value 127 0 0 1 54 Pl sword x 0 0 1 5434 Student M passuword Osp _ _ _ 127 0 0 1 5434 974 _ 127 0 0 1 543 D osp t E DATA E B osp 23 03 2 _ _ 127 0 0 1 5434 5 Press Enter 139 The Pyrrho Book May 2015 Command Prompt osp T p 5434 d A s 0 S 0 EN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 na x ProxyTrans io 0 0 1 5434 _ 5 Enter to start r D 7 Enter to st Enter to Continue to Continue Pha er t About to are _ 0 4 6 o ontinue Enter to Continue to CheckSerialisation _ 127 0 0 1 5434 6 Enter to Continue 1 5 for _ 5 to sta e 2 for _ 5 Enter to start DbStorage Flush complete for B _ _ 127 0 0 1 5434 974 127 0 0 1 5435 974 osp len 105 Enter to start 127 0 0 1 6 Enter tinue _ 5 Enter to start D 7 127 0 0 1 5434 Enter to Continue View OSP gt PyrrhoCmd p 543 ate table E F int primary k E M E DATA E gt A QL gt insert into
49. Client B starts BEGIN TRANSACTION UPDATE Accounts SET balance balance 200 WHERE acctID 202 3 Client A continues UPDATE Accounts SET balance balance 100 WHERE acctID 202 4 Client B continues UPDATE Accounts SET balance balance 200 WHERE acctID 101 5 Client A continues 6 Client B continues COMMIT KH KK KKK KKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKKK In the following we will experiment concurrency anomalies i e data reliability risks known by ISO SQL standard can we identify those z how can we fix the experiments xkxk xkxkx xkxkx xk xkxk xkxkxk xkxkxkxkxkxkxkxk xkxkxkxkxk xkxkxkxkxk xkxkxkxkxkxkxkxkxkxkxkxkxkxkxkxk xkxkxkxkxkxkkk kxxk kxxk Experiment 6 Dirty Read First restoring the original contents by client A 112 The Pyrrho Book May 2015 BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES 101 1000 INSERT INTO Accounts acctID balance VALUES 202 2000 SELECT FROM Accounts COMMIT 1 client A starts BEGIN TRANSACTION SELECT FROM Accounts COMMIT 3 Client A continues ROLLBACK SELECT FROM Accounts Experiment 7 Unrepeatable Read balance 100 WHERE acctID
50. D database And the _Client database is empty The extra entries in the table Database and table Client listings actually show us also the important configuration entries that have been automatically added in the configuration database on A As you can see the server address in each case is that of A Close the session to B with C and let s verify the contents of the configuration database on A PyrrhoCmd p 5434 _ At the SQL gt prompt give the same three commands table _Database table _Client table Sys Table 126 The Pyrrho Book May 2015 We see the same contents in table _ Database and table Client but the SysSTable shows that A has one record in _ Client and one in_ Database gt Thus while the servers agree on the configuration they locally store only their own data the entries for Server 127 0 0 1 5434 are on A and those for 127 0 0 1 5435 are on B You can use Visual Studio to open D osp with the Binary Editor to check that the D osp files match But you can t use the Pyrrho server on B to examine the contents because we have configured it for the Storage role only Close the terminal session with C leaving the terminal window open A4 5 What happened in step 3 In this section we use the special T Tutorial mode of OSP exe to illustrate the steps involved when we created the configuration entry on B with its side effects To get the screenshots in this secti
51. E values 4 7 Share Student 3 items f aa t E DATA B B once again checks D in a new connection This is just possibly theoretically redundant Press Enter again twice E Command Prompt osp T p 5434 d A s 0 S 0 EN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 va x Continue to CheckSerialisation _ 34 6 Enter to Continue Enter to start t to CheckSerialisation _ 127 0 0 1 5434 6 Enter to Continue e 1 5 for _ 5 Enter 2 for _ 5 Enter to st Flush complete for B _ _ 127 0 0 1 5434 974 12 ase 2 to start 0 1 5434 6 Enter to Continue 4 to start g D 7 127 0 0 1 5434 IFlabout to in D 7 Enter to Continue to start Share View O DATA E gt A ssword 127 0 0 1 Student lt 3 items E ie De x t E DATA E gt B sp _ _ 127 0 0 1 5434 D osp We now have the binary replica of D in B s folder Press Enter 140 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 M 0 3 Rollback 3 Ends with 9 5 Protocol byte Prepare Prepare 2 physicals repare rdCs a mplete 5 Protocol byte CheckSerialisation 5 Protocol byte CheckSerialisation 5 Protocol byte Request DbStorage Flush complete for A _ _ 127 0 0 1 Connection 9 Coordinator 127 0 0 1 5435 File 9 Protocol byte RemoteBegin 9 Protocol byte CloseConnec Exception 00000 9 Rollbac
52. Method or Property Explanation DateTime date The underlying DateTime value Date DateTime d Constructor string ToString Overridden Formats the date using DateTime ToShortDate which is locale specific For the embedded editions Pyrrho Common Date is equivalent A9 3 PyrrhoArray PyrrhoConnect Get Post Put Delete can be used for whole Arrays This class can be used to access fields within Documents and to convert to and from Json and XML Note this class remembers the connection to the database if any and all these changes are transacted in the database unless the Document is detached Method or Property Explanation PyrrhoArray object string kind ARRAY or MULTISET void Add int i object data The values of the array or multiset Note that the ordering of multiset values is non deterministic and not significant A9 4 PyrrhoColumn The methods and properties of PyrrhoColumn are Method or Property Explanation bool AllowDBNull Whether the column can contain a null value string Caption The name of the column string DataType The domain or type name of the column bool ReadOnly Whether the column is read only A9 5 PyrrhoCommand PyrrhoCommand implements IDbCommand or imitates ir 207 The Pyrrho Book May 2015 Method or Property Explanation string CommandText The SQL statement for the Command PyrrhoReader Initiates a database SELECT and returns a reader for the Exec
53. Note the sytax of ObjectName given in sec 7 4 above above uses keyword prefixes such as TABLE The COLUMN syntax shown can only be used with tables SquareRoot SQRT Value Y StandardDeviation STDDEV_POP STDDEV_SAMP DISTINCT ALL Value FuncOpt Sum SUM DISTINCT ALL Value FuncOpt Variance VAR_POP VAR_SAMP DISTINCT ALL Value FuncOpt DateTimeFunction CURRENT_DATE CURRENT_TIME LOCALTIME CURRENT_TIMESTAMP LOCALTIMESTAMP StringValueFunction Normalize Substring Substring Regex Translate_Regex Fold Trim Provenance XmlAgg Normalize NORMALIZE Value Substring SUBSTRING Value FROM Value FOR Value SUBSTRING Value SIMILAR Value ESCAPE Value Substring Regex SUBSTRING_REGEX Pattern_Value FLAG Flag Value IN Value FROM StartPos Value USING CHARACTERS OCTETS OCCURRENCE RegexOccurrence_Value GROUP RegexCaptreGroup_ Value Translate_Regex TRANSLATE_REGEX Pattern_Value FLAG Flag Value IN Value WITH Replacement_Value FROM StartPos_ Value USING CHARACTERS OCTETS OCCURRENCE RegexOccurrence_Value GROUP RegexCaptreGroup_ Value Fold UPPER LOWER Value Trim TRIM LEADING TRAILING BOTH character FROM Value Provenance PROVENANCE TYPE_URI Value XmlAgg XMLAGG
54. OWL instead of single quotes as in SQL The type information following the can be an iri or an iri expression using a namespace e g dvla reg or a domain identifier as here Namespaces can be managed in the database using the CREATE XMLNAMESPACES syntax e g CREATE XMLNAMESPACES http dvla gov uk types owl AS dvla DEFAULT http abc com t owl Note the use of single quotes to match the standard SQL2011 syntax for WITH XMLNAMESPACES The default namespace is referenced by using a blank prefix e g Mim The same notation can be used in expressions as a shorthand for a TREAT expression UPDATE cars SET reg reg 4ukregno WHERE country UK 8 4 Row and table subtypes In an INSERT operation whole rows or tables can be assigned a subtype using the TREAT function A structured type can be declared with additional uri information such as CREATE TYPE t AS c CHAR b INT 44 lt http a com gt Then supposing table A had been created with a compatible row type such as CREATE TABLE c CHAR b INT we could write either of the following equivalent forms INSERT INTO A TREAT VALUES Ex 1 AS t INSERT INTO A VALUES Ex 1 44t The type of a row can be tested using the ROW keyword e g ROW IS OF type 76 The Pyrrho Book May 2015 8 5 Provenance In Pyrrho provenance information can be associated with transactions and INSERT operations BEGIN TRANSACTION WITH PROVENANCE iri INSERT WITH PROVENA
55. Partition C149 5 30 50 66 72 94 112 130 149 Partition la ES 324 Record for 66 94 2 130 Two Record 324 E 345 PTransaction for 1 Role 5 User 27 Time 30 03 2015 21 25 06D 327 D2 345 PTransaction2 lo 376 Record for 66 94 2 130 Deux Record 376 ELE At this point SysSTable for D on A and for D2 on B will both show 2 rows in E Again close the session with AC Before we go on let us check what records we have in the two configuration databases We find the one record we placed in the _Partition table on A slightly modified 166 The Pyrrho Book May 2015 E OSP gt PyrrhoCmd p 5434 _ SQL gt table Sys Table a seo Client 4 221 _ Database 7 lo 475 _Partition 14 Name PartitionServer PartitionServerConfigUser PartitionServerConfigPassword Base BaseServer sePassword Table SegmentName Column MinValue MaxValue IncludeMin IncludeMax 127 0 0 1 5435 Student tttttt t terror lE2 True SQL gt C E 10SP gt The changes are that the names E and F for the partitioning table and column have been replaced by the strings 66 and 94 respectively as these are the defining positions in the base partition for these objects Passwords are hidden as usual On B we see a record generated by the Reconfigure process in B s Database table that tells B that D2 is a partition based on D on A E OSP gt PyrrhoCmd p 5435 _ SQL gt table Sys Table Pos Name
56. Paste the following text into the PyrrhoCmd window at the SQL gt prompt on Windows right click the title bar and select Edit gt Paste create table accounts accno int primary key balance numeric 6 2 custname char constraint sufficient_funds check balance gt 0 insert into accounts values 101 456 78 Fred insert into accounts values 103 682 91 Joe table accounts The output should look similar to the following C PyrrhoDB Pyrrho gt pyrrhocmd Bank SQL gt create table accountsCaccno int primary key gt balance numeric 6 2 gt custname char gt constraint sufficient_funds check Chalance gt 1 SQL gt insert into accounts values 161 456 78 Fred gt SQL gt insert into accounts values 183 682 91 Joe gt foe table ac 3 2 Pyrrho s logs and system tables Examine the log Apart from the DOS window wraparound it looks like this SQL gt table Log Pos Desc Type Affects Transaction 4 PRole Bank PRole 0 1 32 Puser MALCOLM NB Malcolm Puser 32 1 55 PTransaction for 9 Role 4 User 32 Time 10 02 2013 16 27 15 PTransaction 0 0 71 PTable ACCOUNTS PTable 71 55 84 PDomain INTEGER INTEGER PDomain 84 55 106 PDomain NUMERIC 6_2 NUMERIC P 6 S 2 PDomain 106 55 134 PDomain CHAR CHAR PDomain 134 55 152 PColumn ACCNO for 71 0 84 PColumn3 152 55 174 PIndex u 56 on 71 152 PrimaryKey PIndex 174 55 195 PColumn BALANCE for 71 1 106 PColumn3 195 55 220 PColum
57. Profiles If profiling is turned on these tables are available profile identity ProfileSReadConstraint ProfileSRecord ProfileSRecordColumn ProfileSTable 205 The Pyrrho Book May 2015 Appendix 9 The Pyrrho Class Library Reference Any application using Pyrrho should include just one of PyrrhoLink dll OSPLink dll EmbeddedPyrhho dll OSP dll xxxOSP dll The following classes are defined SQL2011 API Class Subclass of Description Date Po Data type used for dates PyrrhoArray aa Data type used for ARRAY and MULTISET if a System Data IDbConnectio PyrrhoColumn PyrrhoConnect PyrrhoDocument Pyrrholnterval n column of type ARRAY or MULTISET has been added to the table Helps to describe the columns of a table or structured type Establishes a connection with a Pyrrho DBMS server and provides additional methods and properties This class allows editing of embedded Documents in the sense of MongoDB This class is used to represent a time interval PyrrhoRow Data type used for ROW fields in a database table a column of type ROW can be added to the table SQL2011 Exceptions Class Subclass of Description DatabaseError System Exception Used for user exceptions e g a specified table or column does not exist an attempt is made to create a table or column that already exists incorrect SQL etc The message property gives a readable explanation The SQLSTATE
58. S 0 M BN Command Prompt OSP T d B p 5435 sl BR Command Prompt OSP T d C p 5436 s 0 S 0 M 0 T p 5434 d EZ E OSP gt 0SP T d B p 5435 s 5 0 JE OSP gt 0SP T d C p 5436 s 0 5 0 M 0 0 T d B p 5435 s S M Enter 17 d C p 5436 s 5 0 M Enter to start and UniverPyrrho DBMS c 2015 Malcolm Crowe and Pyrrho DBMS c 2015 Malcolm Crowe and Universi 5 2 19 March 2015 www pyrrhodb com 5 2 19 March 2015 www pyrrhodb com Connecting D 3 127 0 0 1 5434 PyrrhoDBMS protocol on 127 0 0 1 5436 About to Begin D 3 Enter to Continue Database folder C FilesClosed D 3 Enter to Continue PyrrhoDBMS protocol on 127 0 0 1 5435 Database folder B A Home Share View DATA E A a Name Osp D osp lt 2 items 3 B O x T DATA E gt B Name j Date modified Osp 2 D osp 2 lt 2 items E z lite a Name 143 The Pyrrho Book May 2015 A4 8 Creating the query service for D on C In the PyrrhoCmd window PyrrhoCmd p 5436 _ EX Command Prompt osp T p 5434 d A s 0 S 0 M Command Prompt OSP T d B p 5435 s E Command Prompt OSP T d C p 5436 s 0 S 0 M 0 E OSP gt OSP T d B p 5435 s S 0 JE OSP gt OSP T d C p 5436 s S 0 M 0 T d B p 5435 s 0 S 0 M T d C p 5436 s 0 S 0 M 0 Enter to start up and UniverPyrrho DBMS c 2015 Malcolm Crowe and Pyrrho DBMS c 2015 Malcolm Crowe and U
59. Student Temp Statement stmt conn createStatement ResultSet rs stmt executeQuery select from a for boolean b rs first b b rs next System out println rs getInt B rs getString C Note that the public class has the same name as the file You need to remember that Java is case sensitive while SQL isn t so use e g B and C even if you declared your table with lower case names e g create table a b int c char Note that both pyrrhodb and java sql define a Connection class so you can t use above 105 The Pyrrho Book May 2015 Now compile it with javac JCTest java and run it with java JCTest As an exercise try out your own database Note the column names in getInt etc are case sensitive You should be able to do update delete etc using stmt ExecuteNonQuery A1 7 Using PHP with Pyrrho Rename the C Program Files x86 PHP folder to PHP1 Copy the PHP folder in Pyrrho51 iso to Program Files x86 Not in an Administrator command prompt change direct to OSP Install the OSPLink dll in the gacutil C Program Files x86 Microsoft SDKs Windows v8 A bin NETFX 4 0 Tools gacutil i OSPLink dll Register the assembly C Windows Microsoft NET Framework v4 30319 regasm tlb OSPLink dll Now try the PHP version of the above program Get Notepad to put the following in try php lt php conn new COM OSPLink or die Cannot connect conn gt Connectio
60. a combination of optimistic concurrency on the network and pessimistic concurrency in the DBMS All such hybrid solutions really place the responsibility for verifying consistency on the application where it does not really belong We return to this problem in Chapter 5 4 7 Databases and the file system Changes to the database need to be made durable so they need to get written to durable media such as hard disks The simplest possible sort of database file organisation would have a single text file per database These days computer memories are so large that many databases would fit in memory we can almost imagine the whole thing simply being written to disk periodically But in the interests of speed we also have indexes to locate information very quickly and these typically occupy similar amounts of memory to the data itself In the old days computer memories were small so that the data and indexes were kept on disk Pages being modified would be in memory and clever page replacement algorithms would ensure that the disk contents kept pace with changes to the data Pyrrho has a different approach all the indexes are kept only in memory and the disk file consists exactly of the transaction log This makes the committing of a transaction very simple typically a single disk write operation appending the transaction data to the end of the database It is obviously good practice for the DBMS to have exclusive access to th
61. base server so these should occur in explicitly transacted groups each group preceded by Begin Transaction and finished by Commit so that Pyrrho can enforce validation non overlapping at the end of each group when it is also determined what records need to transfer between partitions or to from the base database Table segments should move in their entirety Four situations are supported for at most one base database at a time a Anew partition or new table or segment for an existing partition has been added without any changes to other partitions and some records may transfer from the base database to the new partition b One or more configuration rows for a partition P has been deleted No updates to other rows records affected will move to the base database c Changes to other partitions that may now receive tables or segments from P d Split of a single TableSegment no records need to move between partitions It should be possible to design any change in partitioning as a sequence of these four steps Note that movement of records happens after each validation step so the transacted group only has to match one of the above 92 The Pyrrho Book May 2015 References Ceri S Pelagatti G 1984 Distributed Database Design Principles and Systems McGraw Hill Cheung A Arden O 2012 Automatic Partitioning of Database Applications Proceedings of the VLDB Endowment 5 p 1471 1482 Codd E F 1985 Does
62. because of lock timeout or transaction conflict there are two options redesign of the task or scheduling it to take place during maintenance periods Pyrrho includes a mechanism for diagnosing incidents where database transactions fail Generally a transaction T has a read a set Rr of data items and is committing changes to a set W of data items and typically these sets overlap With optimistic concurrency control transactions are unaware of concurrent transactions but a transaction commit will fail if another transaction has committed a change to any data item in Rr UWz To analyse such failures Pyrrho assists with aggregating failures of this type using a supplemental log that records the read and write details for each transaction along with the success or failure of the transaction 5 8 Profiling implementation If profiling is turned on for a database Pyrrho maintains a transaction profile which is persisted not in the database itself but in an XML file this is because it is a record not of the entire database activity but just the periods for which profiling is enabled Profiles can be deleted without harming the database in any way There is a convenience utility called ProfileViewer which displays the profile in a readable tree view format The profile can either be fetched from the server assuming profiling is enabled or loaded from the XML file in which case ProfileViewer expects to find the xml file in its worki
63. coding things you can do Add a textbox and a ComboBox to the form Populate the combobox from the database table you can do this any time e g after you change the database comboBox Items Clear var cmd new MySqlCommand select from member conn var rdr cmd ExecuteReader while rdr Read 96 The Pyrrho Book May 2015 comboBox1 Items Add rdr 1 7 Click the datagradview1 and double click the SelectionChanged event In the event handler add the following code if dataGridView SelectedCells Count gt 0 textBox1 Text dataGridView1 SelectedCells 0 Value ToString 8 Declare aclass internal class Myltem public int val public string str public Myltem int v string s val v str s public override string ToString return str 9 Change the comboBox1 Items Add line above to comboBox1 Items Add new Myltem int rdr 0 string rdr 1 10 In the designer click the combo box and double click the SelectedValueChanged event In the handler give the code var it comboBox1 Selecteditem as Myltem if it null MessageBox Show it val ToString og club Running Microsoft Visual Studio Quick Launch Ctrl Q Po P x FIL ag Form1 lel T ANALYZE WINDOW HELP ua ot A E ya comboBoxl_SelectedValueChanged object sender EventArgs e E r EventArgs e ToString internal class MyItem t public int val public string str E public override
64. configuration file B _ osp has been created But instead of an ordinary LocalTransaction the server has started a special Reconfigure transaction In the B server window use the Enter key four times Command Prompt osp T p 5434 d A s 0 S 0 E Command Prompt OSP T d B p 5435 s 0 S 0 M 0 5 CTE Enter to s up owe and University of the West of Scotland Ib com 75435 complete f Commit for tid 2 4 Enter to start 4 Enter to start 2 for _ 4 Enter to 3 for _ 4 Enter to start IStartCommit for osp at 34 bStorage Flush complete f Phase 4 for _ 4 Enter to EM Command Prompt PyrrhoCmd p 5435 _ rrhoCmd p 5434 D table E F int primary key i rt into E val 4 7 Home Share View O DATA E A k SP gt PyrrhoCmd p 5435 _ i 5 insert into _Database values D 127 0 0 1 5435 assword 0 1 5434 Student D osp We see that the configuration database has grown to 979 bytes to accommodate the three empty tables _Database _Client and _Partition Now press the Enter key to start phase 4 E Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d B p 5435 s 0 S 0 M 0 osp len 39 4 Enter r _ 4 Enter Enter to start Enter to start _ osp len 979 Home Share View lO DATA E A insert into 127 0 0 1 5434 S word D osp E DAT
65. confused Serious transactions should use the API instead of the command line 13 The Pyrrho Book May 2015 Chapter 2 Data Consistency Transparency and Durability When people speak of databases consistency transparency and durability are three of the main properties they ought to expect But in database software it has very strangely become normal to support inconsistency and undermine the efforts of software engineers to provide reliable systems in a mistaken pursuit of speed at all costs It is not clever to base any decisions on incorrect data so getting a wrong answer before your competitors is no real advantage In this book we assume that inconsistency is always bad since every database starts out in a consistent state it is the job of the DBMS to prevent inconsistencies from creeping in Companies almost always store the data for their business processes customers employees accounts etc in databases Interestingly the data in company databases often is retained for decades long after the computer systems used to create then have ceased to exist Legacy data still needs to be accessed Although computer books often refer to the corporate database it is rare now for a company to have just one But any of these corporate databases can be accessed by numerous other computers and programs in the company or its various branches or customers and database management systems need to be able to cope with many concurrent connec
66. create the partition s on the remote server but of course does not display these The Column field can be a selector dot separated names for accessing data within a document or user defined structured type Each partition holds all rows in the configured partitioned tables that match the value bounds specified For each table the segments thus defined must be non overlapping and this property is checked at the end of a reconfiguration transaction Accordingly if several partitioning records in the configuration database are being changed it is important to wrap the steps into an explicit transaction The following reconfiguration transactions are supported New Segment Split Segment Move Segment and Delete Segment so the sequence of steps must allow the group to be classified as one of these operations Automatically the process of commiting the resulting transaction will move records out of and or into partitions as required The changes to the configuration database must be made on the base server by the owner of the base database who must therefore have at lreast temporary permission to modify the base server s configuration database 91 The Pyrrho Book May 2015 If a transaction changes data in more than one partition a link between the two partitions is formed so that both partitions must be available for verification when the database is loaded It is possible to place an entry in the configutaion database to mark a database
67. database role Selector Processing 69 The Pyrrho Book May 2015 Selector matches table Table_id procedure Procedure_id Parameters where Co umn_id string select Column_id Column_id key string of Table_id Column_id Column_id of Table_id Table_id Appending another selector is used to restrict a list of data to match a given primary key value or named column values or to navigate to another list by following a foreign key or supply the current result as the parameters of a named procedure function or method The of keyword is used for reverse navigation of foreign key relationships and for navigating many many relationships the column list if present is for choosing a foreign key or secondary table See examples below Processing matches distinct Column_id Column_id ascending Co umn_id Column_id descending Column_id Column_id skip nt_string count nt_string The Http https Accept and Content Type headers control the formatting used At present the supported formats are XML text xml HTML text html only for responses and SQL text plain The Pyrrho distribution includes a REST client which makes it easier to use PUT POST and DELETE A URL can be used to GET a single item a list of rows or single items PUT an update to a list of items POST one or more new rows for a table or DELETE a list of rows Thus GET and POST are very different operations
68. defined views or generated columns could even have specific data types targeting specific roles since they impose no overhead unless they are explicitly used Roles that are granted usage of an object will not see any subsequent name changes applied in the parent role but the role administrator can define new names Stored procedures view definitions generation rules etc use the definer s permissions for execution If the code is examined in the different roles that use them objects will be referred to using the viewing role s names If such embedded code refers to objects inaccessible to the viewer the code will be reported as definer s code Apart from object names only the owner of an object can modify objects ALTER This includes changes to object constraints and triggers and inevitably such modifications can disrupt the use of the object by other roles procedures etc References in code in other roles can introduce restrictions on dropping of objects but as usual cascades override restrictions and in Pyrrho revoking privileges always causes a cascade Granting select on a table must include at least one notnull column Granting insert privileges for a role must include any notnull columns that do not have default values and cannot include generated columns An example We walk through a simple database example about a library database Either start up the PyrrhoSQL client as shown 60 The Pyrrho Book May 2015
69. either before or after the value For example if the above domain definition was modified to create domain watts as real W units watt where units stands for http sweet jpl nasa gov 1 1 units owl then allowable literals would include both 2 37 Aunits watt and 2 37 W Note the different use of respectively double and single quotes here and the optional white space in the string single quoted version When adding rows or assigning values involving such types values of the correct subtype should be provided or expressions with compatible base types explicitly coerced to match the declared type of the column or variable so that in the above example the real literal 2 37 could not be used to give a value for a column declared as type watts In cases where a value is already a subtype of the required type the subtype information is retained and even persisted in the database For value expressions the TREAT function can be used to coerce a value to a subtype and in Pyrrho the notation can be used as a shorthand for this e g a b watts Otherwise Pyrrho s type system is as in SQL2011 with the following changes a char and char 0 indicate unbounded strings int int 0 integer and integer 0 indicate 2048 bit integers see example in the section above and real has a mantissa of 2048 bits by default b size specific standard types 75 The Pyrrho Book May 2015 such as bigint or double are not supported c p
70. entries in the log LogSEdit Details for EDIT records in the log LogSGrant Details for GRANT records in the log LogSIndex Details for INDEX records in the log when indexes are created LogSIndexKey Details for keys of indexes LogSInsert Details for INSERT records in the log LogSInsertField Details for fields in INSERT records LogSMetadata Details of METADATA entries in the log LogS Modify Details of MODIFY entries in the log LogSOrdering Details of user defined orderings LogS Procedure Details of user defined procedures LogSRevoke Details of REVOKE records in the log LogSTable Details of metadata for user defined tables LogSTablePeriod Details of table period definition LogSTransaction Details of all transactions in the Log LogSTransactionParticipant Details of participants for distributed transactions LogSTrigger Details of user defined triggers LogSTriggerUpdateColumn Update column details for user defined triggers LogSType User defined types See also LogSDomain and LogSTypeMethod LogSTypeMethod Details of methods defined for user defined types LogSUpdate Details of UPDATE records in the log LogSUser Details of USER records in the log LogSView Details of VIEW definitions in the log ROWS nnn Details of operations involving table defined at nnn in the log ROWS rrr ccc Details of operations involving the table cell at the row defined at rrr and column defined at ccc in the log
71. for that connection user role and maybe other per database stuff and the server spawns a new thread for the connection so that the connection is local to the thread If streams are opened to remote servers then these will access a new connection thread on each remote server connected to Thus the connection has a thread local list of databases tailored to the connection details Complete isolation is maintained between threads and therefore transactions No changes are made to the global database list until commit see below Although all of the versions of the database share the same local or remote datafile changes are merely cached until commit at which time only the transaction master actually writes new data to the datafile other storage files are updated during sync 4 Ifa database is partitioned there are two situations a the connection is to the base database and the partitions are silently added to the connection b the connection is to a partition and the base database is silently added to the connection 5 Within the connection there will be transactions for each connected database there will be a corresponding localtransaction with its own evolving database schema and set of proposed changes Distributed transactions affect all levels of the DBMS so even storage needs to be transacted 6 Local transactions allow SQL queries in all cases too such as examination of system tables processing of new data for databases a
72. from a MongoDB collection a query consists of a Json object with a set of key value pairs the result set is the set of documents in the collection that match these properties The properties are not limited to equality conditions This is a very powerful and attractive way of selecting data from large distributed collections and much to be preferred over standard SQL in many cases Mongo does not use SQL does not support transactions it does claim strict consistency and does not have mechanisms for creating joins have begun to develop a MongoDB service offered by the Pyrrho server that when complete will offer full ACID guarantees on top of the full Mongo service It will do this by running on the Pyrrho database engine enhanced as necessary The enhancements turn out to be very exciting as extensions to SQL SQL already allows columns in relational tables to contain structured types and XML data It is exciting to allow integrity and 31 The Pyrrho Book May 2015 referential constraints to apply to fields within such structured objects For example in any document collection the _id key is the primary key it is a field within the JSON object With Codd s principles in mind Pyrrho allows extensions to SQL to support embedded JSON so that anything that can be done using the Mongo service can also be done using the resulting extended SQL including the construction of document sets First steps in Pyrrho Pyrrho provides a Mong
73. geographical basis can spread the load between transaction masters This can enable higher throughput provided transactions that use data from more than one partition are very rare as even a small number of distributed transactions can cause serious delays Transaction profiling can help to identify useful choices of partitions e g see Curino et al 2011 We return to consider distributed databases in Chapter 8 Despite all the theory and despite some very well publicised disasters few business people accept the need for a single transaction master for each database fragment or the need to stop all transactions if the network becomes partitioned 5 5 ADO NET and transactions It is rather important to understand that ADO NET 2 0 introduced two parallel mechanisms of operation with different concurrency mechanisms e The DataSet and DataAdapter types used a disconnected data model based on optimistic concurrency e The DbCommand and DataReader types used pessimistic concurrency Because only one DataReader can be open for a given database connection this all works in a fairly natural way the duration of locking is the length of time that the data reader is open We can make local changes to a DataSet and when we try to commit them to the database ADO NET makes a new transaction for us and checks that the affected records are still the same as when we read them 5 6 Versioning From April 2015 Pyrrho has a type of row versioning which
74. identifier is permitted any action granted to it directly or through arole An authorisation identifier is enabled if it is the current user identifier the current role name or the name of a role that is applicable for the current role A privilege is current if it is applicable for an enabled authorisation identifier In Pyrrho DBMS only one role is current at any point in a session A user authorisation identifier must choose a single role as the session role and can modify this within the session using the SET ROLE statement to another role they have been granted Thus in Pyrrho the only enabled authorisation identifiers are the current user name and the current role 6 7 The role stack During query execution any invoked operation is checked to see that the current role has been authorised to carry out the operation at the start of the analysis the current role is set to the session role When the operation involves transferring control to a routine and the current role is permitted to execute the routine the current role becomes the role of the routine the definer s role and is restored on exit from the routine When the transaction is committed all of the modifications will be recorded against the original user s id and the session role When reviewing such a record it is important to remember that the changes may have been made by a routine operating with different permissions 57 The Pyrrho Book May 2015 In P
75. important than speed Alternatives to the relational model are included in this book where relevant it is a misconception that the failings of database products are somehow the fault of the relational model or SQL This book will take for granted the concerns of introductory texts such as the relational design SQL entity relationship modelling joins and triggers One of these concerns normal form data is notable here in that it contributes to database correctness since any duplication of data has a potential for inconsistency It represents an efficiency trade off since with normal form the information for the domain needs to be reconstructed by recombining data from these extra tables or selecting columns from larger tables and where normalisation is reversed for efficiency reasons it is at the cost of repairing duplicates for example with the help of triggers These considerations are of interest but they come before the starting point for this book we assume good database design Our concerns begin with such issues as transaction non isolation the suspending of constraints or inadequate transactional guarantees In fact the most serious criticism of existing commercial products relates to ACID properties and implementation of transactions wherein many cases they don t follow their own documentation When this book is used in a university course would strongly recommend including the Transactions tutorial from DBTechNET org
76. in the HTML so that it can supply CSS style or script If the string begins with lt it should be an XSL transform and Pyrrho will generate and then transform the return data as XML HTML responses will have JavaScript added to draw the data visualisations specified 121 The Pyrrho Book May 2015 Appendix 4 The Distributed Database Tutorial for Windows The exercise follows the blog at http pyrrhodb blogspot com just with more detailed instructions This version of the tutorial uses Open Source Pyrrho v5 2 19 March 2015 on Windows 10 If you can get a later version use it Pyrrho has been installed in E OSP You will probably use C A4 1 Start up the servers For this exercise we will use 3 servers all on the local machine 127 0 0 1 but in separate database folders Create empty folders NA B and C To keep security aspects simple everything is owned by the user Student and student s password is password In the following screenshots these folders are in E We will use 3 file manager windows so we can see the contents of these foldersFor the 3 servers we will use 3 command windows and a fourth for the command line processor All will use the same folder OSP On the first we issue the following commands cd OSP OSP d A p 5434 s 0 S 0 M 0 The s S and M flags prevent the server starting the http https and Mongo services as we would need to allocate non conflicting ports for these The arguments ar
77. not find out that there is a conflict until just before you write the updated data In pessimistic locking you find out there is a conflict as soon as you try to read the data To use an analogy with banks pessimistic locking is like having a guard at the bank door who checks your account number when you try to enter if someone else a spouse or a merchant to whom you wrote a check is already in the bank accessing your account then you cannot enter until that other person finishes her transaction and leaves Optimistic locking on the other hand allows you to walk into the bank at any time and try to do your business but at the risk that as you are walking out the door the bank guard will tell you that your transaction conflicted with someone else s and you will have to go back and do the transaction again With pessimistic locking the first user to request a lock gets it Once you have the lock no other user or connection can override your lock SQL Server s optimistic concurrency uses versioning they call it snapshot isolation When a record in a table or index is updated the new record is stamped with the transaction sequence_number of the transaction that is doing the update The previous version of the record is stored in the version store and the new record contains a pointer to the old record in the version store Old records in the version store may contain pointers to even older versions All the old versions of a particul
78. null values 29 The Pyrrho Book May 2015 3 6 LINQ Language Integrated Query was an innovation in C 3 0 Ling allows queries of the sort var queryl from t in things where t Cost gt 300 select new t Owner Name t Cost to be written directly in CH The Pyrrho support for Linq is therefore inspired by the idea of supporting queries to simple small databases and avoiding declarations and annotations wherever possible The client side objects can be modified using the methods in sec A9 6 but queries should always be to a new connection The Ling support is only for single component primary keys they can be any scalar type and do not have be called Id The following complete program works with a database called home which contains two tables with the following structure create table Person Id int primary key Name char City char Age int create table Thing Id int primary key Owner int references Person Cost int Descr char Then the RoleSClass system table see Appendix 8 provides text for the two class definitions as below The PyrrhoConnect connects to the database as usual and the database is opened Two PyrrhoTable lt gt declarations form a link between client side data and data in the home database Then the LINQ machinery is available For the program to produce output there needs to be some data in the tables using System using System Collections Generic using
79. of the MULTISET constructor syntax and if row valued must be part of the TABLE constructor syntax above Collate if specified applies to an immediately preceding Boolean expression affecting comparison operands etc HTTP GET gives a string value by default unless used within an INSERT statement in which case Pyrrho will attempt to convert to the expected row type The mime string is used for retrieval of a particular content type from the server QueryExpression and VALUES give a Table_Value whose type is contextually determined The AS syntax above is allowed only in parameter lists and methodcalls A mongo_spec is like the comma separated key value list in a JavaScript objects Json keys are case sensitive and are enclosed in single or double quotes and values are numerics or single or double quoted strings or regular expressions or embedded JavaScript objects or arrays enclosed in Strings starting with have special meanings and can be used in Selectltems to refer to values in the curret context e g Sa b BinaryOp Y IE MultisetOp is used in array and string concatenation VariableRef Scope_id Variable_id ColumnRef TableOrAlias_id ColRef TableOrAlias_id PROVENANCE CHECK The use of the PROVENANCE and CHECK pseudo columns is a change to SQL2011 behaviour CHECK is a row versioning cookie derived from a string type MultisetOp MULTISET UNION INTERSECT EXCEPT ALL
80. of the transaction log records and the concept of data type is defined at level 2 Transaction isolation is handled in the Pyrrho DBMS engine by using immutable data structures up to level 3 database of the design Up to this level all fields of data structures are at least logically constant so that for example any change made to a linked list or B tree results in a new head node When a transaction is committed the data is serialised to the data file s and the new head nodes for the database s affected will be installed in the list of databases connected to the server Each ongoing transaction level 4 uses a separate space of proposed database objects so that the objects being defined within them have temporary positions above 0x40000000 and these numbers are only unique within that ongoing transaction At the start of transaction copies are made of the head node of each database in the transaction effectively this takes a snapshot of the database at the start of the transaction and the transaction proceeds on the basis of this starting database state Committing a transaction requires serialising the transaction to the data file transaction log and the defining positions of objects are not known until this is done During serialisation these are relocated to their actual positions in the data file transaction log The actual process of committing a transaction takes place in 3 stages In stage 1 the connected datafiles are che
81. only to the database owner via SQL queries through the use of system tables as described in Chapter 8 2 of this manual It is of course possible to use such automatically recorded data in databases and applications In other ways Pyrrho supports investigation For example in SQL2011 renaming of objects requires copying of its data to a new object In Pyrrho by contrast tables and other database objects can be renamed so that the history of their data can be preserved From version 4 5 object naming is role based see section 3 6 The logo on the front cover of this book combines the ancient Greek key design used traditionally in architecture with the initial letters of Pyrrho and suggests security in its interlocking elements 2 1 Durability Of the trio of topics mentioned in the chapter heading Durability looks the easiest we assume that we want to keep data in a good form and our business operations need to be recorded properly Of course the resulting values of data account balances etc will be modified later on as a result of our business processes so that durability means that we should be able to show later that the data had this value today Strangely very few database systems really have the durability property When values are deleted or modified there is usually no way to recover the values that were there before Some commercial systems support a transaction log but there are no mechanisms to require it to be ke
82. refingtable e The deleted key as a linked list of values e A pointer to the next ReferenceDeletionConstraint Concurrency control for referential constraints for insertions records are handled by ReferencelnsertionConstraint level 2 It is done at level 2 for speed during transaction commit and consists of a linked list of the following data which is stored in a non persisted field of the Record record e The set of key columns in the referenced table e The defining position of the referenced table reftable e The new key as a linked list of values e A pointer to the next ReferencelnsertionConstraint For distributed databases all the above checking information needs to be sent to the transaction master for verification 52 The Pyrrho Book May 2015 Chapter 6 Role Based Security In any organisation the allocation of responsibilities to individuals varies over time and so it makes sense to assign permissions not to individual users but to roles Roles are associated with business processes not job descriptions any one individual might be assigned a number of roles in different business processes such as validate travel expenses assign salesman to region publish telephone directory It is a good idea to have a number of roles if there are none than there is no traceability and no security anyone can do anything and nobody will ever know why It is also a good idea that every operation on a database declares the role bein
83. start 4 Protocol byte Prepare to Prepare _ 127 0 0 1 5435 6 Enter to Continue sPrepare 1 physicals to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Coni Record p I 1 5 for _ 9 Enter to start Prepare 0 rdCs to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con Prepare complete E 1 5 for _ 5 Enter to start 4 Protocol byte CheckSerialisation 2 for _ 5 Enter to start 4 Protocol byte CheckSerialisation ppstorage Flush complete for C _ _ 127 0 0 1 5435 1137 _ 127 Phase 2 for _ 9 Enter to start EN Command Prompt PyrrhoCmd p 5436 _ Home Share View rt into D 127 0 0 1 DATA E A p Name osp _ D osp 2 items 1 DATA E gt B Name Date modified 1 D osp 2 items 1 DATA E C Name Osp L _ _ 127 0 0 1 5435 1137 _ 127 0 0 1 54 We see that C server has written a temporary transaction data file to the C folder Press Enter again twice 148 The Pyrrho Book May 2015 E Command Prompt osp T p 5434 d A s 0 S 0 M BN Command Prompt OSP T d B p 5435 s _ fa Command Prompt OSP T d C p 5436 s 0 S 0 M 0 4 Protocol byte IndexNext 1 Coordinating Commit for tid 1 4 Protocol byte IndexLookup Reconfigure 4 Protocol byte IndexNext RemoteTransaction D 2 Protocol byte CloseConnection ProxyTransaction _ 127 0 0 1 5435 Exception 00000 Phase 1 for _ 5 Enter to start 2 Rollback Phase
84. string ToString return str public MyItem int v string s val v str s o private void comboBox1_SelectedValueChanged object sender EventArgs e t var it comboBox1 SelectedItem as MyItem if it null MessageBox Show it val ToString Chi INS 18 03 09 01 2014 a Pe 92 E 97 The Pyrrho Book May 2015 A1 2 Using SQL Server Compact Edition 1 You can use the local database bundled with Visual Studio as a kind of SQL Server lite Create a new Windows Forms application with Visual Studio Right click the Project in Solution Explorer and then Add gt New Item click Data select Local database DataSet and then confirm opening of the empty database 2 View Server Explorer and expand the connection to the new database right click Tables and select Create Table In the New Table dialogue give the table name as Member add the columns we want and set the Primary Key Similarly create the Played table for the Boolean field use bit 3 Create the foreign key references by opening the Table Properties and selecting Add Relations Give WinnerFK as the relation name and select winner as the Foreign Key Table column Add Columns then Add Relation and confirm Repeat for loserFK and click OK to close the dialogue Note the default action is NO ACTION which is ridiculous 4 To place data in the tables right click the tables and select Show Table Data When you enter the da
85. the groups You can see my solution in the resources gt Gah for this text The beginning of the code for the application shows how it works Note the declaration of the PyrrhoConnection and the code for creating and opening the connection highlighted in yellow When we need data from the database we use ADO NET incantations one example is highlighted in green The transaction to do the funds transfer is highlighted in grey and notice how it is surrounded with an exception handler Using Pyrrho namespace WpfApplication2 lt summary gt Interaction logic for MainWindow xaml lt summary gt public partial class MainWindow Window public MainWindow InitializeComponent Account2 Visibility Visibility Hidden class AcInfo public int id public string name public AcInfo int i string n id i name n public override string ToString AcInfo selected null other null private void Account1_DropDownOpened object sender EventArgs e Var cmd db CreateCommand return name The Pyrrho Book May 2015 Account1 Items Clear private void Account1_SelectionChanged object sender SelectionChangedEventArgs e selected Account1 SelectedItem as AcInfo if selected null var cmd db CreateCommand cmd CommandText select balance from accounts where accno selected id var rdr cmd ExecuteReader if rdr Read Amo
86. the program As before we need to implement updates In the designer left click the DataGridView select the Events tab in the properties window and double click RowValidated repeat for CellValidated and RowEnter Add declarations in the Form1 class for bool newRow false int id bool cellChanged new bool 3 Enter the following code in the event handlers private void dataGridView1_RowValidated object sender DataGridViewCellEventArgs e var r dataGridView1 Rows e RowIndex var cm if newRow cm insert into members values r Cells Value ToString r Cells 1 Value ToString r Cells 2 Value ToString newRow false else var s 7 var c 5 if cellChanged s c id r Cells 0 Value ToString cat if cellChanged 1 s c firstname r Cells 1 Value ToString eatr if cellChanged 2 s c surname r Cells 2 Value ToString c 3 if s cm update members set s where id id if cm try conn Act cm catch private void dataGridView1_RowEnter object sender DataGridViewCellEventArgs e var r dataGridView1 Rows e RowIndex if r null 88 newRow amp amp r Cells Value null 104 The Pyrrho Book May 2015 int TryParse r Cells Value ToString out id for int j j lt 3 j cellChanged j false private void dataGridView1_CellVal
87. the same time How database servers manage this is crucial In order to preserve consistency we cannot see a jumble of half done transactions when we look at a database Transactions as we will see need to be atomic To achieve consistency and atomicity we could lock parts of the database in advance delaying conflicting transactions until we are done pessimistic or we could simply allow all transactions to proceed in isolation only identifying conflict when transactions commit optimistic Either way the database server programming will be complicated As mentioned above on big installations there will be many servers The scenario that a request might be handled by any of them is quite common but there is an option to place different databases on different clusters of servers Large databases might be partitioned so that data is spread over many servers We will consider later in the course the different ways that servers can cooperate on managing a database Viewing this problem from the viewpoint of the application we note that on the Internet the traditional pessimistic solution of transactions locking the resources they are considering updating is widely considered unsuitable and most vendors have settled for a concept of eventual consistency e g see Elbushra and Lindstr m 2014 relying on compensation methods for resolving conflicts e g Lessner et al 2012 Most application frameworks designed for the Web use
88. this folder and is called _ It contains tables with names starting with _ The basic schema of _ is hardwired in the server engine so that _ is created the first time the server owner alters a configuration table By default the configuration tables are empty databases that are not mentioned in the configuration tables are local databases and we know about no other servers In this way we already have an API for configuration namely SQL ADO NET and we conform to Codd s rule that SQL should be the DDL for the DBMS Configuration tables holding server data are automatically partitioned so that each _ database only holds information for data managed by that server instance and is the transaction master for its own data Thus any change to properties of remote servers is handled as a remote update the Pyrrho protocol already supports this It turns out that the provision for verification of distributed transactions is exactly what is required to guarantee consistency of the information held by different servers When the server starts up it should load the _ database if present What will be new is a more elegant handling of the situations where servers are unavailable obviously this should mean that their databases and partitions are unavailable Code exists in the server already for deferring distributed transaction verification and this is exactly what is needed for if and when the remote server comes online later See also Database de
89. to Continue About to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Cd Share View e a p 5436 _ sd MISOL gt insert into _Database values D 127 0 0 1 5436 password 127 0 0 1 5435 student DATA E A password Name Da Press Enter Command Prompt osp T p 5434 d A s 0 S 0 M EEN Command Prompt OSP T d B p 5435 EM Command Prompt OSP T d C p 5436 OSP gt osp T p 5434 d A s S 0 M 0 Connection 4 Coordinator 127 0 0 1 5434ppstorage Flush complete for C _ osp len 979 T p 5434 d 5 0 S 0 Enter to sta Protocol RemoteBegin Phase 4 for _ 4 Enter to start Pyrrho DBMS c 2015 Malcolm Crowe and Unive Protocol IndexLookup 3 ti Committed 5 2 19 March 2015 www pyrrhodb com Protocol IndexNext Connecting D 5 127 0 0 1 5435 PyrrhoDBMS protocol on 127 0 0 1 5434 Protocol IndexLookup About to Begin D 5 Enter to Continue Database folder A Protocol IndexNext Connecting _ 127 0 0 1 5435 127 0 0 1 5435 Connection 2 Coordinator 127 0 0 1 5435 Fileg Protocol CloseConnection 127 0 0 1 5435 6 Enter to Continue 2 Protocol byte RemoteBegin Exception 00 1 Coordinating Commit for ti 2 Protocol byte CloseConnection 2 Rollback Reconfigure Exception 90000 About to Close D 5 Enter to Continue RemoteTransaction D 2 Rollback Closed D 5 Enter to Continue ProxyTransaction 127 0 0 1 5435 2 Ends with 9 2 Ends with 9 Phase 1 for _ 5 Enter to start
90. transaction E Command Prompt OSP T p 5434 d A s 0 S 0 M 0 onnecting D2 13 127 0 0 1 5435 About to Begin D2 13 Enter to Continue connecting _ 127 0 0 1 5435 14 127 0 0 1 5435 About to Begin _ 127 0 0 1 5435 14 Enter to Contin 7 Coordinating Commit for tid 6 Reconfigure _ LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 1 for _ 12 Enter to start 1 for D 13 Enter to start 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue to CheckSerialisation D2 13 Enter to Continu 1 for _ 17 Enter to start to Prepare _ 127 0 0 1 5435 14 Enter to Cont to CheckSerialisation _ 127 0 0 1 5435 14 En 173 Command Prompt OSP T p 5435 d B s 0 S 0 M 0 omplete b The Pyrrho Book May 2015 After a few more Enters we see the completion of checking and the saving of transaction data 3 phase commit on A for the configuration part EN Command Prompt OSP T p 5434 d A s 0 S 0 M 0 Command Prompt OSP T p 5435 d B s 0 S 0 M 0 ProxyTransaction _ 127 0 0 1 5435 di ol byte IndexNext 1 for _ 12 Enter to start sical 1 for D 13 Enter to start 1 al 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue to CheckSerialisation D2 13 Enter to Continue 1 for _ 17 Enter to start to Prepare _ 127 0 0 1 5435 14 Enter to Continue to CheckSerialisation _ 127 0 0 1 5435 14 Enter to Continue 1 5 for _ 12 Enter to start 1 5 for _ 17 Enter to star
91. updates because Pyrrho maintains a full historical record It is helpful to separate data comprising the historical record from ad hoc or transient analysis files so Pyrrho has a multi database connection mechanism to facilitate connecting to more than one database at a time Currently PyrrhoSvr exe is approximately 870KB and when running the server process starts out with about 12MB of memory but requires approximately as much additional memory as the size of the database file Memory RAM is required only for current data so if many records in the database have been deleted or much of the database file consists of updates the working memory required will be less than the size of the database file Pyrrho is intellectual property of the University of the West of Scotland United Kingdom The associated documentation and source code where available are copyright of the University of the West of Scotland Your use of this intellectual property is governed by a standard end user license 2 However it is a good idea to have a separate folder for the databases It is simplest to copy the server executable to the folder you plan to use See section 1 2 3 It is best to provide exactly one of these four dlls in folders containing client executables We no longer recommend installing components in the global assembly cache 8 The Pyrrho Book May 2015 agreement which permits the uses described above without charges All other use requires a
92. value has no retrospective effect since there are no null values to apply it to ViewDefinition VIEW id AS QueryExpression UPDATE SqlStatement INSERT SqlStatement DELETE SqlStatement Metadata This is an extension to SQL2011 syntax to provide simpler mechanisms for indirect tables Note that all of these can use Web services to access remote data TriggerDefinition TRIGGER id BEFORE INSTEAD OF AFTER Event ON id RefObj Trigger In Pyrrho triggers can be defined on views this is very useful when used with roles Event INSERT DELETE UPDATE OF id id RefObj REFERENCING OLD NEW ROW TABLE AS id In this syntax the default is ROW TABLE cannot be specified for a BEFORE trigger OLD cannot be specified for an INSERT trigger NEW cannot be specified for a DELETE trigger Trigger FOR EACH ROW STATEMENT TriggerCond Statement BEGIN ATOMIC Statements END 186 The Pyrrho Book May 2015 TriggerCond WHEN SearchCondition DropStatement DROP DropObject DropAction DropObject ObjectName ORDERING FOR id l ROLE id TRIGGER id l XMLNAMESPACES id DEFAULT id DEFAULT l INDEX id DropAction RESTRICT CASCADE The default DropAction is RESTRICT Rename SET ObjectName TO id A6 3 Access Control Grant GRANT Privileges TO GranteeList WITH GRANT OPTION GRANT Role_id Role_id TO GranteeList WITH ADMIN OPTION
93. where the where clause contains a document value will be propagated efficiently into the relevant partitions and will retrieve only the records where the documents match Moreover indexes can use document field values 36 The Pyrrho Book May 2015 Document matching recurses down to matching of fields and then may involve comparisons of say 4 with Sgt 3 so care is taken in the coding that this is implemented as a comparison of Sgt 3 with 4 rather than the other way around so that Document comparison occurs Documents are always retained in memory as in MongoDB and during updates the modifying Document is stored in the database while the modified document is only in memory The PhysBase keeps track of the documents by indexes for colpos recpos gt Document and Objectld gt Document Documents in memory contain no reserved keys apart from Sid A document containing Sid is a DBRef and when this is referenced the second index above is used to retrieve the referenced document SqlDataType Strong types are used internally for all transaction level processing The main mechanism for this is the SqlDataType It provides methods of input and output of data parsing coercing checking assignability etc Domain constraints are applied at Level 2 i e at the point where a a Record or Update is being prepared for serialisation to the physical database but they can use level 3 information e g lookup tables implemente
94. with 9 1 tid 1 Committed Home Share View 0 1 DATA E A Name Close the session in the PyrrhCmd window with C 150 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 E Command Prompt OSP T d B p 5435 s 0 S EN Command Prompt OSP T d C p 5436 s 0 S 0 M 0 DbStorage Flush complete for C _ _ Phase 2 for _ 9 Enter to start t to Request 27 0 0 1 Enter to Continue hase 3 for _ 5 Connecting D 5 127 0 0 5 About to Begin D 5 Enter to Continue 4 StartCommit for _ osp at 974 Protocol byte c 6 Protoco Remo i DbStorage Flush complete for osp len 1142 Protoce e r n R nit e 3 for D 7 Enter to start 3 3 _ 9 Enter to start About to Commit _ 127 0 0 1 5435 6 Enter to Co Closed _ 127 0 0 1 5435 6 Enter to Continue P 4 for _ 5 Enter tc t 4 for D 7 Enter to start Closed D 5 Enter to Continue Phase 4 _ 9 Enter to start 1 tid 1 Committed 1 Ends with 1 Home Share View t E DATA E A a Name _ osp D osp lt 2 items De o t E DATA E B Name Date modified LJ osp LJ D osp lt 2 items Ec x t E DATA E C Name osp A4 9 What happened in Step 7 At this stage server C is running and has set up all its data structures and indexes to provide a query service for D In the PyrrhoCmd window let us connect to this service Py
95. 01 11000 202 12000 pas emer SQL gt Unsolved problems Why the function return an empty string CREATE PROCEDURE TransferTest fromAcct INT toAcct INT amount INT IF BankTransfer 101 202 100 OK THEN COMMIT ELSE 117 The Pyrrho Book May 2015 ROLLBACK ND IF E BEGIN TRANSACTION SELECT BankTransfer 101 202 100 FROM DUAL 118 The Pyrrho Book May 2015 Appendix 3 Roles and Security A3 1 The sporting club 1 Recall that in Lab 1 we set up the following tables in a database called club Members id int primary key firstname char Played id int primary key winner int references members loser int references members agreed boolean with the following commands create table members id int primary key firstame char surname char insert into members values 56 Fred Bloggs insert into members values 78 Mary Black create table played id int primary key playedon date winner int references members loser int references members agreed boolean insert into played values 32 date 2014 01 09 56 78 false 2 For simplicity we give everyone select access to both these tables Grant select on members to public Grant select on played to public 3 Although Pyrrho records which user makes changes it will save time if users are not allowed to make arbitrary changes to the Play
96. 015 whose type must match the rowset returned by the URL If the array has more than one row commas can be used as separators XML format can also be used which should match the data format returned by the URL POST http Sales Sales Orders will create one or more new rows in the Orders table In Pyrrho an integer primary key can be left unspecified In SQL text plain format column names can be included in the row format e g NAME Fred DoB date 2007 10 22 if no names are provided all columns are expected Remember that the REST service is case sensitive for database object names XML format can also be used in which case column values for the new row can be supplied either as attributes or child nodes irrespective of the data model A mime type of text csv has been added to facilitate import from Excel spreadsheets If no Selector or Processing components are provided the target is the Role itself For this target GET returns a set of C class definitions for POCO use as described in section 3 6 There are some extra columns in the LogS table the record type a related previous log entry if any and the start of the transaction For simplicity we will continue to use the example database from the last two postings with the following additional steps These create a new role Web with read only access to the tables and some metadata for XML formatting of the output The details are given at the end of this section
97. 1 Oxff giving the length as 1 and the data as 1 Otherwise leading O and 1 bytes in the data are suppressed Within the DBMS the most commonly used integer format is long 64 bits and Integer is used only when necessary With the current version of the client library integer data is always sent to the client as strings of decimal digits but other kinds of integers such as defining positions in a database lengths of strings etc use 32 or 64 bit machine specific formats The Integer class in the DBMS contains implementations of all the usual arithmetic operators and conversion functions Decimal All numeric data stored in the database uses this type which is a scaled Integer format an Integer mantissa followed by a 32 bit scale factor indicating the number of bytes of the mantissa that represent a fractional value Thus strictly speaking decimal is a misnomer since it has nothing to do with the number 10 but there seems no word in English to express the concept required Normalisation of a Decimal consists in removing trailing O bytes and adjusting the scale Within the DBMS the machine specific double format is used With the current version of the client library numeric data is always sent to the client in the Invariant culture string format The Decimal class in the DBMS contains implementations of all the usual arithmetic operations except division There is a division method but a maximum precision needs to
98. 1 for D 7 Enter to start About to Close D 5 Enter to Continue about to Close D 5 Enter to Continue losed D 5 Enter to Continue losed D 5 Enter to Continue 2 Ends with 9 P 1 for _ 9 Enter to start 4 Protocol byte Prepare to Prepare _ 127 0 0 1 5435 6 Enter to Continue repare 1 physicals to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con 1 5 for _ 9 Enter to start to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con Prepare complete 1 5 for _ 5 Enter to start 4 Protocol byte CheckSerialisation 2 for _ 5 Enter to start 4 Protocol byte CheckSerialisation ppstorage Flush complete for C _ _ 127 0 0 1 5435 1137 _ 127 4 Protocol byte Request Phase 2 for _ 9 Enter to start PbStorage Flush complete for B _ _ 124qpout to Request _ 127 0 0 1 5435 6 Enter to Continue Phase 3 for _ 5 Enter to start E Command Prompt PyrrhoCmd p 5436 _ into _ DATA E A Name Osp D osp 2 items T DATA E gt B Name Date modified LJ osp L _ _ 127 0 0 1 5435 D osp lt 3 items T DATA E C osp 23 e and Univer 2 Protocol byte CloseConnection RemoteTransaction D Exception 00000 ProxyTransaction _ 127 0 0 1 5435 2 Rollback Phase 1 for _ 5 Enter to start About to Close D 5 Enter to Continue phase 1 for D 7 Enter to start RS About to Close D 5 Enter to Continue 2 Ends with 9 Closed D 5 Enter to Continue 4 P
99. 127 Enter to Continue o 1 5434 11 Enter to Continue moteBegin r 0 1 5434 11 Ent mnection b Seriali De127 1 5434 11 Enter Enter to Continue p 2 for D 11 Enter o Continue About to Request D 127 11 Enter to Conti 11 Enter to Contin Enter to Continue or D 11 Enter to start D 127 0 0 1 11 127 0 0 1 5434 1 5434 11 Enter to Continue 0 0 1 5434 11 Enter to Continue committed fte ExecuteReader 34 11 127 0 0 1 5434 1 5434 11 Enter to Continue Home Share View E DATA E A Name Osp D osp lt 2items 1 item selected 208 bytes Be E DATA E gt B Name Date modified osp D osp lt 2items 1 item selected 179 bytes ic El to E DATA E C Name 0sp After 3 Enters in the C server window we have 157 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S Bi Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Phase 3 for D 11 Enter to start 0 0 1 5434 11 Enter to Continue Enter to Continue rt 0 1 5434 Enter to Continue o Continue 127 0 0 1 5434 Enter to Continue ES Enter ntinue a a seReader it for tid 5 Home Share View e t E DATA E gt A Name L osp _ D osp lt 2items 1 item selected 208 bytes gz Be t E DATA E gt B Name Da
100. 13 Enter to Continue 5 Protocol byte CloseReader 5 Coordinating Commit for tid 3 RemoteTransaction D Phase 1 for D 10 Enter to start Home Share View 17 T DATA E A student Name E LJ osp _ D osp lt 2 items B gt O T DATA E B Name Date modified osp 23 03 201 6 _ D osp 23 6 2 items DATA E C a Notice that data is fetched only from B In B s and C s windows press Enter more times to finish the read only commit 153 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 EH Command Prompt OSP T d B p 5435 5 0 S EN Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Connectin 0 0 1 5435 i Enter to Continue Connecting D 9 127 8 About to Begin RemoteTransaction D Phase 1 for D 10 Enter to start About to Close D 9 En to Continue Closed D 9 Enter to Continue 3 for D 10 Enter to start 4 for D 10 En 1 5435 Enter to Continue r to Continue tid 3 Committed Home Share View 0 E DATA E A Name Osp _ D osp 2 items De e t E DATA E gt B Name Date modified osp LJ D osp e t E DATA gt C Name osp Let s now watch what happens when we make a change from C the change needs to get made by the master server A not by B SQL gt insert into E values 8
101. 2 Committed 2 Rollback 2 Protocol byte Fetch Connecting D 5 127 0 0 1 5435 2 Ends with 9 2 Protocol byte Fetch About to Begin D 5 Enter to Continue Connection 4 Coordinator 127 0 0 1 5435 FilegConnection 4 Coordinator 127 0 1 5434connecting 5435 6 127 0 0 1 5435 4 Protocol byte RemoteBegin Protocol byte RemoteBegin About to Begin _e 1 5435 6 Enter to Continue Protocol byte IndexLookup 1 Coordinating Commit for tid 1 Protocol byte IndexNext IES Protocol byte IndexLookup RemoteTransaction D Protocol byte IndexNext ProxyTransaction _ 127 0 0 1 5435 Phase 1 for 5 Enter to start 3 Coordinating Commit for tid 2 EX Command Prompt PyrrhoCmd p 5436 _ Fie Home Share ERRE OSP gt PyrrhoCmd 5436 _ SQL gt insert into _Database values D 127 0 0 1 54 password 127 0 1 5435 student DATA E A password Name D Osp Now we see that C is coordinating a distributed reconfiguration transaction checking the configuration database on B like B did to A in the previous section Press Enter 3 times EM Command Prompt osp T p 5434 d A s 0 Command Prompt OSP T d B p 5435 sl ER Command Prompt OSP T d C p 5436 s 0 OSP gt osp T p 5434 A s 0 5 0 M 0 Closed D 3 Enter to Continue T p 5434 d A s 0 0 Enter to starPyrrhoDBMS protocol on 127 0 0 1 5435 Pyrrho DBMS c 2015 Malcolm Crowe and UniverDatabase folder B 5 2 19 March 2015
102. 2015 static Add ref T Key Value For the given tree T add entry Key Value static Update ref T Key Value For the given tree T update entry Key to be Value static Remove ref T Key For the given tree T remove the association for Key Note that even where words like Update are used any Tree is immutable in particular the Update operation returns a new Tree sharing many of its immutable elements with the old one Immutable trees of this sort are shareable Pyrrho has two mutable B Tree types these are Multiset and RTree These are not shareable For multivalued tree types see below an additional parameter can be supplied to the last two methods e g Static ATree lt K V gt Update ref T Key OldValue Value This replaces the association Key OldValue with Key Value there may be other values for the given Key Treelnfo There are many different sorts of B Tree used in the DBMS The Treelnfo construct helps to keep track of things especially for multilevel indexes which are used for multicolumn primary and foreign keys Treelnfo has the following structure Name Description SqlDataType kType Defines the type of a compound key SqlDataType vType The type of values indexed using the tree TreeBehaviour onDuplicate How the tree should behave on finding a duplicate key The options are Allow Disallow and Ignore A tree that allows duplicate keys values provides an additional tr
103. 3 2015 22 16 On the next Enter on A A starts a new connection 5 to the configuration database on B so B starts to create this Since there are three empty tables to add to the new configuration database we need five Enters in B s window It is probably an unnecessary complication that A is coordinating two separate remote transactions on B At the moment servers create new remote connections for each remote database in a distributed transaction Possibly a future version of Pyrrho will enable the coordinating server to open a multi database connection on any remote server in the transaction 171 The Pyrrho Book May 2015 EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EN Command Prompt OSP T p 5435 d B s 0 S 0 M 0 7 Protocol byte ExecuteReader DbStorage Flush compl for A _ osp len 39 10 Coordinating Commit for tid 8 Reconfigure Phase 1 for _ 11 Enter to start ase 1 5 for _ 11 Enter to start 11 Enter to start 11 Enter to start iStartCommit for _ osp at 34 DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 11 Enter to start et Committed connecting D2 13 127 0 0 1 5435 bout to Begin D2 13 Enter to Continue connecting _ 127 0 0 435 14 127 0 0 1 e Home Share View t E DATA E gt A d 2 items I D2 osp L osp The next Enter on A s window begins the commit for the distributed transaction Reconfigure on A a ch
104. 5434 5 Protocol byte ExecuteReader About to Begin D 11 Enter to Continue Connecting D 5 127 0 0 1 5435 About to Begin D 5 Enter to Continue B Command Prompt PyrrhoCmd p 5436 D e 1 DATA E A Name osp D osp 152 The Pyrrho Book May 2015 and in C s window press Enter once EN Command Prompt osp T fH Command Prompt OSP T d B p 5435 s 0 S 0 M 0 Command Prompt OSP T d C p 5436 s 0 S 0 M 0 About to Begin D 9 Enter to Continue About to Begin D 5 Enter to Continue 6 Protocol byte RemoteBegin StartCommit for _ osp at 974 4 Protocol byte RemoteCommit DbStorage Flush complete for C _ osp len 1142 1lstartCommit for _ osp at 1137 Phase 3 for D 7 Enter to start DbStorage Flush complete for B _ osp len 1282 Phase 3 for _ 9 Enter to start 4 Ends with 31 About to Commit _ 127 0 0 1 5435 6 Enter to Continue 6 Protocol byte CloseConnection Closed _ 127 0 0 1 5435 6 Enter to Continue Exception 00000 Phase 4 for _ 5 Enter to start 6 Rollback Phase 4 for D 7 Enter to start llabout to Close D 9 Enter to Continue Closed D 5 Enter to Continue Closed D 9 Enter to Continue Phase 4 for _ 9 Enter to start 6 Ends with 9 1 tid 1 Committed Connection 8 Coordinator 127 0 1 5436 Files D Role Use 1 Ends with 1 Connecting D 11 127 0 0 1 5434 Connection 5 Files D User asusrog Student About to Begin D 11 Enter to Continue 5 Protocol
105. 8 In 194 Insert 189 IntegerType 188 Intersect 196 IntervalField 189 193 IntervalQualifier 193 The Pyrrho Book May 2015 IntervalType 189 ItemName 197 JoinedTable 191 JoinType 191 Label 198 Last 195 LengthExpression 195 Like 194 Like Regex 194 Literal 192 LobType 188 Locale 211 LoopStatement 198 Maximum 195 Member 184 194 Metadata 121 184 Method 182 MethodCall 198 MethodType 183 Minimum 195 Modulus 195 MultisetOp 192 NamedValue 198 Namespace 198 NamespaceDefault 198 NaturalLogarithm 195 Next 195 Normalize 196 Null 194 Nullif 195 NumericType 189 NumericValueFunction 194 ObjectName 187 ObjectPrivileges 187 Occurrences_ Regex 195 of 70 Of 194 Open 198 OrderByClause 191 Ordering 185 OrderSpec 191 OrdinaryGroup 190 Parameter 183 Parameters 182 PartitionClause 190 Percentile 195 PeriodBinary 194 PeriodName 186 Port 211 Position 195 Position_Regex 195 PowerFunction 195 Predicate 193 PreiodPredicand 194 Privileges 187 Provenance 196 Provider 211 PyrrhoArray 206 207 PyrrhoConnect 206 Pyrrholnterval 206 209 214 PyrrhoRow 206 209 210 QueryExpression 189 QueryExpressionBody 189 QueryPrimary 189 QuerySpecification 189 QueryTerm 189 Rank 195 ReferentialAction 186 RefObj 186 Regression 195 Rename 187 Repeat 198 Representation 185 ResetReader 209 Revoke 187 RollCube 190 Routine 188 RowNumber 1
106. 95 Schema 195 SearchCondition 191 Selectltem 189 SelectList 189 SelectSingle 198 Set 196 SetAuthority 209 SetFunction 196 Signal 197 Similar 194 SimpleTable 189 Some 194 Sql 181 SqglStatement 181 SquareRoot 196 StandardDeviation 196 StandardType 188 StartField 193 Statement 181 Statements 198 StringValueFunction 196 Subquery 191 Substring 196 Substring_Regex 196 Sum 196 TableClause 185 TableConstraint 186 TableConstraintDef 186 TableContents 185 TableExpression 189 TableFactor 190 TablePeriodDefinition 186 TableReference 190 Target 197 TicksPerSecond 209 TimePeriodSpecification 191 TransactionConflict 206 Translate_Regex 196 Trigger 186 TriggerCond 187 TriggerDefinition 186 Trim 196 The Pyrrho Book May 2015 Type 188 Typecast 196 TypedTableElement 186 Unique 194 UpdatePositioned 189 UpdateSearched 189 UriType 185 UserFunctionCall 198 Value 191 Values 186 VariableRef 192 Variance 196 VersioningClause 185 ViewDefinition 186 WhereClause 190 While 198 WindowBetween 190 WindowBound 190 WindowClause 190 WindowDef 190 WindowDetails 190 WindowFrame 190 215 WindowSpec 195 WindowStart 190 WithinGroup 195 XmlAgg 196 XmlColumn 191 XmlColumns 191 XMLComment 198 XMLConcat 198 XMLDec 197 XMLDocument 198 XMLElement 198 XMLForest 198 XMLFunction 198 XMLNDec 183 XMLOption 183 XMLParse 198 XMLProc 199 XMLQuery 1
107. 979 Phase 4 for _ 11 Enter to start 10 tid Committed ng D2 13 127 0 0 1 5435 About to Begin D2 13 Enter to Continue b 5 y h co e _ osp len 979 connecting _ 127 0 0 1 5435 14 127 0 0 1 5435 About to Begin _ 127 0 0 1 5435 14 Enter to Contin 7 Coordinating Commit for tid 6 Reconfigure _ LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 Phase 1 for _ 12 Enter to start hase 1 for D 13 Enter to start 3 more enters and we see the Prepare step for B A sends no physicals to B just now 172 The Pyrrho Book May 2015 EN Command Prompt OSP T p 5434 d A s 0 S 0 M 0 tartCommit for _ osp at 34 DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 11 Enter to start 190 tid 8 Committed onnecting D2 13 127 0 0 1 5435 About to Begin D2 13 Enter to Continue onnecting _ 127 0 0 1 5435 14 127 0 0 1 5435 bout to Begin _ 127 0 0 1 5435 14 Enter to Contin 7 Coordinating Commit for tid 6 Reconfigure _ LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 1 for _ 12 Enter to start 1 for D 13 Enter to start 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue to CheckSerialisation D2 13 Enter to Conti Enter on A CheckSerialisation succeeds EN Command Prompt OSP T p 5434 d A s 0 S 0 M 0 DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 11 Enter to start 10 tid 8 Committed connecting D2 13 127 0 0 1 5435 About to B
108. 99 XMLText 199 XMLValidate 199 XSL 73 121
109. A E B Osp 133 The Pyrrho Book May 2015 A4 6 A distributed transaction begins The user has requested that a new record is added to the configuration database The Reconfigure class overrides the AddRecord method to watch out for references to remote databases D on A in this case as these will need entries in the configuration database on the remote server At the point shown in the screenshot we have identified a reference to a new local D connected to a remote D onA At the start of phase 4 server B begins to coordinate a distributed transaction and contacts server A In the above screenshot we see server A has acknowledged a connection for database D from server B and server B is about begin to create database D This connection is no 3 on server A and no 5 on server B Press Enter EM Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 y of the West of Scotland Home Share View t E DATA E A Name _ D osp The Begin for D involves getting the contents of database D from A which we see in the Fetch message in A s window B can now write these contants in its LocalSlave database D and will do so when it closes D below B creates a second connection to server A to A s configuration file _ 127 0 0 1 5434 as connection 6 A acknowldeges this new connection as 5 and creates an empty coniguration d
110. A s 0 S 0 M 0 EN Command Prompt OSP T p 5435 d B s 0 S 0 M 0 p 5434 d A s 5 0 M Enter to start up MO OSP p 5435 d B s 0 S 0 M 0 yrrho DBMS c 2015 Malcolm Crowe and University of n 5 2 27 March 2015 www pyrrhodb com gt yrrhoDBMS protocol on 127 0 0 1 5434 j h y Database folder MAN P pro 2 C IE OSP gt OSP T p 5434 d A s 0 5 0 M 0 T p 5434 d A s S 0 M 0 Enter to start up yrrho DBMS c 2015 Malcolm Crowe and University of 2 27 March 2015 www pyrrhodb com Py rrhoDBMS protocol on 127 0 0 1 5434 Database folder A onnection 1 Files D User asusrog Student 1 Protocol byte ExecuteReader DbStorage Flush complete for A D osp len 55 1 Coordinating Commit for tid 1 LocalTransaction D Phase 1 for D 5 Enter to start lela O Home Share View nt G char prir E DATA E gt A A Name _ D osp In A s window press the Enter key 5 times to complete the commit and get the next SQL gt prompt in the command window 169 The Pyrrho Book May 2015 EN Command Prompt OSP T p 5434 d A s 0 S 0 M 0 IS O x EM Command Prompt PyrrhoCmd p 5434 D Share View Om DSP oP to E DATA gt A Name D osp You can see that server A has been dealing with a connection 1 to database D by Student created an empty database D osp in the A folder of length 55 bytes just role and user information and the 5 phases of committing the tran
111. AT TOOLS TEST ANALYZE WINDOW HELP O aa A un 0 z No Source Available MANS MainWindow xaml cs amp MainWindow g i cs amp 80 86 Jx m m 9 lt G Design tt El XAML lt Window x Class clubwPF MainWindow xmlns http schemas microsoft com winfx 20 xmlns x http schemas microsoft com winfx Title MainwWindow Height 35 Width 525 gt E lt StackPanel Height 319 VerticalAlignment Top E lt Grid Name Members Loaded Grid_Loaded_1 gt E lt Grid ColumnDefinitions gt lt ColumnDefinition Width 97 gt lt ColumnDefinition Width 1508 gt lt ColumnDefinition Width 270 gt lt Grid ColumnDefinitions gt lt Grid gt E lt StackPanel Orientation Horizontal gt lt TextBox Name idBox Width 80 gt lt TextBox Name fnBox Width 308 gt lt TextBox Name snBox Width 80 gt lt Button Name adBtn Width 8 Content Add Click adBtn_Click gt lt StackPanel gt lt StackPanel gt 100 The Pyrrho Book May 2015 clubWPF MainWindow WD Grid_Loaded_1 object sender RoutedEventArgs e private void adBtn_Click object sender RoutedEventArgs e ZE var cmd conn CreateCommand cmd CommandText insert into member values idBox Text fnBox Text snBox Text cmd ExecuteNonQuery idBox Text fnBox Text snBox Text Refresh void Refresh i var cmd conn CreateCommand cmd Command
112. C D B would be no different to Files A B C D With the use of operating system integrated user identities the user identity can be expected to be valid in all databases involved in the connection Roles are a different matter Generally at most one of the databases will be modified in any transaction and the Role string chosen for the connection should be the correct one for such a modification It is not expected or required that role identifiers in different databases should match in any way There are some limitations on usage in such multi database connections 89 The Pyrrho Book May 2015 e All data definition drop and access control statements affect only the local database e Object integrity cannot create dependencies on other databases generally schemas must not contain references to other databases This means for example that new referential constraints can only be specified where the referenced table is in the local database On the other hand subtypes including uri based subtypes are constructed in the receiving database as needed when data from another database is inserted in the local database Data manipulation can affect all databases in the connection provided the connection string specifies this It is relatively unusual for a single transaction in a multi database connection to result in changes in more than one database for example in the above scenario with four databases at most one would be modifi
113. CT FROM T COMMIT BEGIN TRANSACTION DELETE FROM T WHERE id gt 1 COMMIT Testing the database Recovery BEGIN TRANSACTION INSERT INTO T id s VALUES 9 Let s see what happens if SELECT FROM T lt close the client gt He rea 222 gt 2 gt gt 2 22 gt 2 gt 2 225 2 gt gt 2 gt gt gt 3 gt 222 gt 2 gt gt o gt gt gt o2 gt P 2 Starting a new terminal window and connecting to our TestDB we can study what happened to our latest uncommitted transaction Just by listing the contents of table T Pyrrho Client cd opt OSP mono PyrrhoCmd exe TestDB 109 The Pyrrho Book May 2015 SELECT FROM T COMMIT don t regard closing the client and restarting it as database Recovery what do you think Experiment 1 COMMIT and ROLLBACK in session of client A Pyrrho Client cd opt OSP mono PyrrhoCmd exe TestDB BEGIN TRANSACTION CREATE TABLE Accounts acctID INTEGER NOT NULL PRIMARY KEY balance INTEGER NOT NULL CONSTRAINT uncreditable account CHECK balance gt 0 INSERT INTO Accounts acctID balance VALUES 101 1000 INSERT INTO Accounts acctID balance VALUES 202 2000 SELECT FROM Accounts COMMIT let s try the bank transfer BEGIN TRANSACTION UPDATE Accounts SET balance balance
114. Connection 4 Coordinator 127 0 0 1 5435 Fileg 4 Protocol byte Pre Phase 1 for D 7 Enter to start 4 Protocol byte RemoteBegin Prepare 1 physicals About to Close D 5 Enter to Continue 4 Protocol byte CloseConnection Record Closed D 5 Enter to Continue Exception 00000 Prepare rdCs Phase 1 for _ 9 Enter to start 4 Rollback Prepare complete About to Prepare 1 5435 6 Enter to Continue 4 Ends with 9 4 Protocol byte CheckSerialisation About to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Co Phase 1 5 for 9 Enter to start EX Command Prompt PyrrhoCmd p 5436 _ File Fiii da Vana OBIE OSP gt PyrrhoCmd p 5436 _ A insert into Database values DATA E gt A We see that C is organising a distributed commit with B Press Enter again twice 147 The Pyrrho Book May 2015 EM Command Prompt osp T p 5434 d A s 0 S 0 M_E Command Prompt OSP T d B p 5435 sil E Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Protocol RemoteBegin Protocol IndexLookup Connecting D 5 127 0 0 1 5435 Protocol IndexNext About to Begin D 5 Enter to Continue Protocol IndexLookup Connecting _ 127 0 0 1 5435 6 127 0 0 1 5435 Protocol IndexNext About to Begin _ 127 0 0 1 5435 6 Enter to Continue Protocol CloseConnection 1 Coordinating Commit for tid 1 Reconfigure _ RemoteTransaction D About to Close D 5 Enter to Continue proxyTransaction _ 127 0 0 1 5435 Closed D 5 Enter to
115. Continue Phase 1 for _ 5 Enter to start 2 Ends with 9 Phase 1 for D 7 Enter to start 4 Protocol byte Prepare About to Close D 5 Enter to Continue Prepare 1 physicals Closed D 5 Enter to Continue Record 1 for _ 9 Enter to start Prepare 0 rdCs to Prepare _ 127 0 0 1 5435 6 Enter to Continue Prepare complete to CheckSerialisation _0127 0 0 1 5435 6 Enter to Con 4 Protocol byte CheckSerialisation 1 5 for _ 9 Enter to start 4 Protocol byte CheckSerialisation g to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con 1 5 for _ 5 Enter to start Share View lt DATA E A Name In Phase 1 5 we repeat the check serialisation with the databases locked Press Enter again twice EX Command Prompt osp T p 5434 d A s 0 S 0 M EN Command Prompt OSP T d B p 5435 s l Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Protocol RemoteBegin Connecting _ 127 0 1 5435 6 127 0 0 1 5435 Protocol IndexLookup About to Begin _ 127 0 0 1 5435 6 Enter to Continue Protocol IndexNext 1 Coordinating Commit for tid 1 Protocol IndexLookup Reconfigure Protocol IndexNext RemoteTransaction D Protocol CloseConnection ProxyTransaction _ 127 0 0 1 5435 Phase 1 for _ 5 Enter to start 7 Phase 1 for D 7 Enter to start About to Close D 5 Enter to Continue lanout to Close D 5 Enter to Continue Closed D 5 Enter to Continue Closed D 5 Enter to Continue 2 Ends with 9 1 for _ 9 Enter to
116. E E es ee carve ace foes paca E acto onetae ae 81 Chapter 9 Distributed Databases oomomssss 83 9 1 Distributed transactions c sscsccecistsescigahavcivisndvaccansagueedscevedoashonacds e Eata EE Ee aaraa 83 92 Dynamic CON OU AU on zeii aeea a E e a ENRETA 84 9 3 Auto partition algorithm for A 85 9 4 ComectionMana 2er di 85 9 5 Database Dependencia EAEE R cisne 86 9 0 Cooperating e usse a e satu geen a a 87 9 7 Transaction implementation sseessssessessseesseeessseessetssessetsssessseesstesseesseeesseeesseesseesse 87 Chapter 10 Partitioned Databases sessesossoesessossesossossesossossessossesossossesossossesoossesossosseseso 89 10 1 Multiple database connections pi A A a Did 89 is AA eS Gh ead oN sls CR ee a 90 WO Database Partonin sanis cco tora dah OS 91 10 4 Parution sequence a as 92 al PENA A A 92 LG O EOS 93 Appendix 1 Using ADO NET for various databases sesessossesossossesoosoesossossesossossesoososse 95 ES A nn avai e a T a e E item aira a ianetela 95 A1 2 Using SQL Server Compact Eqitton gies scsscassisseecssoscas es cseedanasdasatevansccedesccsaactdevedavese 98 A1 3 Using SqlServerCe with basic ADO NET 1 0000 ec eeeceesceesseceeescceeeecceesscceeneceeeseeeees 99 A1 4 Using SQL Server Ex press visiiiin rta nica aia cios 101 ATS Using PyrbhoD teens io e ii 102 A1 6 Using Java with Pyrrhons rassinn otrs e sse is E Eii 105 The Pyrrho Book May 2015 Acls7 Using PHP swith Pyrrhon A ean ie ete E
117. EMA SCHEMA_NAME SERVER_NAME SPECIFIC_NAME SUBCLASS_ORIGIN TABLE_NAME TRIGGER_CATALOG TRIGGER_NAME TRIGGER_SCHEMA SQLSTATE strings are 5 characters in length comprising a 2 character class and and a 3 character subclass See the table in section 8 1 1 Fetch FETCH How Cursor_id INTO VariableRef VariableRef How NEXT PRIOR FIRST LAST ABSOLUTE RELATIVE Value ForStatement Label FOR For_id AS id CURSOR FOR QueryExpression DO Statements END FOR Label_id IfStatement IF BooleanExpr THEN Statements ELSEIF BooleanExpr THEN Statements ELSE Statements ENDIF Label label LoopStatement Label LOOP Statements END LOOP Open OPEN id Repeat Label REPEAT Statements UNTIL BooleanExpr END REPEAT SelectSingle QueryExpresion INTO VariableRef VariableRef Statements Statement Statement While Label WHILE SearchCondition DO Statements END WHILE UserFunctionCall Id Value Value MethodCall Value Method_id Value Value Y Value AS Type Y Method_id Value Value Y Type Method_id Value Value Y A6 10 XML Support XMLFunction XMLComment XMLConcat XMLDocument XMLElement XMLForest XMLParse XMLProc XMLQuery XMLText XMLValidate XMLComment XMLCOMMENT Value XMLConcat XM
118. L2011 but currently there is no difference A6 5 Data Manipulation Insert INSERT WITH PROVENANCE string XMLOption INTO Table_id Cols Table_Value For example is INSERT INTO t VALUES 4 5 or is INSERT INTO t SELECT c d FROM e UpdatePositioned UPDATE XMLOption Table_id Assignment WHERE CURRENT OF Cursor_id UpdateSearched UPDATE XMLOption Table_id Assignment WhereClause DeletePositioned DELETE XMLOption FROM Table_id WHERE CURRENT OF Cursor_id DeleteSearched DELETE XMLOption FROM Table_id WhereClause CursorSpecification XMLOption QueryExpression FOR READ ONLY UPDATE OF id id A simple table query is defined SQL2011 02 14 1SR18c as a CursorSpecification in which the QueryExpression is a QueryTerm that is a QueryPrimary that is a QuerySpecification QueryExpression QueryExpressionBody OrderByClause FetchFirstClause QueryExpressionBody QueryTerm QueryExpression UNION EXCEPT ALL DISTINCT QueryTerm DISTINCT is the default and discards duplicates from both operands QueryTerm QueryPrimary QueryTerm INTERSECT ALL DISTINCT QueryPrimary DISTINCT is the default QueryPrimary SimpleTable QueryExpressionBody OrderByClause FetchFirstClause SimpleTable QuerySpecification Value TABLE id QuerySpecification SELECT ALL DISTINCT SelectList TableExpression SelectList Selectltem Selectltem
119. LCONCAT Value Value Y XMLDocument XMLDOCUMENT Value XMLElement XMLELEMENT NAME id Namespace AttributeSpec Value Y Namespace XMLNAMESPACES NamespaceDefault string AS id string AS id Y NamespaceDefault DEFAULT string NO DEFAULT AttributeSpec XMLATTRIBUTES NamedValue NamedValue NamedValue Value AS id XMLForest XMLFOREST Namespace NamedValue NamedValue Y XMLParse XMLPARSE CONTENT Value 198 The Pyrrho Book May 2015 XMLProc XMLPI NAME id Value XMLQuery XMLQUERY Value xpath_xml This syntax seems to be non standard in Pyrrho but allows extraction from an xml Value using an XPath expression XMLText XMLTEXT xml XMLValidate XMLVALIDATE DOCUMENT CONTENT SEQUENCE Value 199 The Pyrrho Book May 2015 Appendix 7 Pyrrho s condition codes Standard SQL exception handling allows stored procedures to set up handlers for various conditions that arise in the database engine The SQL standard specifies a number of these but most in the list below are specific to Pyrrho Diagnostic information about the causes of the condition is also available through use of the GET DIAGNOSTICS mechanisms SQLSTATE 01010 02000 0U000 21000 21101 22000 22003 22004 22005
120. Log 10 The Pyrrho Book May 2015 In SQL2011 table id isthesameas select from id for base tables and system tables Your output will differ in a number of respects from this e g your folder will probably not be E OSP and some explanations are important here as we can see the Windows identity of the user that started PyrrhoCmd not the server Normally the PyrrhoCmd command line will have an argument parameter indicating the database s to connect to If none is given PyrrhoCmd will open or create a database called Temp You can confirm this by looking in the server s folder you will see a file called Temp pfl or Temp osp it was not there before Pyrrho creates a default Role for the database with the same name as the database and records the identity of the creator user this will be your login ID All later entries in the log file will have transaction information You can use control C or close the window to exit from PyrrhoCmd If you want to delete the database file that you have just created you will need to stop the server When starting up PyrrhoCmd the following command line arguments are supported database One or more database names on the server The default is Temp Do not include the osp or pfl file extension h hostname Contact a server on another machine The default is localhost p nnnn Contact the server listening on this port number The default is 5433 sS Silent suppress warnin
121. N TRANSACTION Accounts having balance gt 1000 euros SELECT FROM Accounts WHERE balance gt 1000 2 Client B starts BEGIN TRANSACTION INSERT INTO Accounts acctID balance VALUES 303 3000 SELECT FROM Accounts COMMIT 3 Client A continues Let s s the results SELECT FROM Accounts WHERE balance gt 1000 COMMIT Experiment 9 Update Phantom First restoring the original contents by client A BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUI I S 101 1000 202 2000 ES ES NSERT INTO Accounts acctID balance VALUI ELECT FROM Accounts COMMIT 1 client A starts BEGIN TRANSACTION Accounts having balance gt 1000 euros SELECT FROM Accounts WHERE balance gt 1000 2 Client B starts BEGIN TRANSACTION UPDATE Accounts SET balance balance 2000 WHERE acctID 101 SELECT FROM Accounts COMMIT 3 Client A continues Let s s the results SELECT FROM Accounts WHERE balance gt 1000 COMMIT Notel Multi line commands need to be enclosed in brackets Note2 COMMIT is not allowed in a procedure function The following test is copied from the Pyrrho manual and works fine CREATE TABLE A A2 CHAR 1
122. NCE iri INTO t VALUES data Potentially therefore each record in a database could have two items of provenance information one specific to the record and one specific to the import transaction If both are specified the record iri should have the form of a relative iri A pseduocolumn PROVENANCE was also added so that queries can retrieve or select on the provenance information and the value in this pseudocolumn is the result of concatenation of the transaction and record provenances if any or the uri associated with a row subtype These features are preserved for backwards compatibility and convenience 8 6 Interationalisation In SQL for the convenience of users time values without specified time zones are assumed to be local This approach is easy to criticise after all the client and server are frequently in different time zones Accordingly in Pyrrho any time value without a specified timezone is assumed to be coordinated universal time UTC and this is how it is stored in the database DateTime SQL specifies its own special syntax for dates and times but on output from the database Pyrrho uses the operating system s regional settings and or the conventions of the target language such as C to represent the datetime Keyword Meaning YEAR Year MONTH Month within year DAY Day within month HOUR Hour within day MINUTE Minute within hour SECOND Second and possibly fraction of a s
123. Prepare complete P E DbStorage Flush complete for C _ _ 127 0 0 1 5435 1137 _ 12 4 Protocol byte CheckSerialisation Phase 2 for _ 9 Enter to start 4 Protocol byte CheckSerialisation About to Request _ 127 0 0 1 5435 6 Enter to Continue 4 Protocol byte Request Phase 3 for _ 5 Enter to start DbStorage Flush complete for B _ _ 12 Connecting D 5 127 0 0 1 5435 Connection 6 Coordinator 127 0 0 1 5434apnout to Begin D 5 Enter to Continue Connecting D 9 127 0 0 1 5434 StartCommit for _ osp at 974 Connection About to Begin D 9 Enter to Continue DbStorage Flush complete for C _ osp len 1142 6 Protocol byte RemoteBegin Phase 3 for D 7 Enter to start Phase 3 for _ 9 Enter to start osp at 1137 About to Commit _ 127 0 0 1 5435 6 Enter to Continue DbStorage Flush complete for B _ osp Icjoseq _ 127 0 0 1 5435 6 Enter to Continue 4 Ends with 31 x Phase 4 for _ 5 Enter to start 6 Protocol byte CloseConnection Phase 4 for D 7 Enter to start Closed D 5 Enter to Continue e Phase 4 for _ 9 Enter to start About to Close D 9 Enter to Continue 1 tid 1 Committed Closed D 9 Enter to Continue o 1 DATA E A a atabase values D 127 assword 12 Name osp D osp 2 items gt T DATA E B Name Date modified osp D osp 2 items T DATA E C Name osp We now have the SQL gt prompt in the PyrrhoC
124. Pyrrho CHAR uses standard culture independent Unicode NCHAR is no longer supported and is silently converted to CHAR UCS_BINARY is supported The SQL2011 standard specifies a locale neutral interface language to the server for example using a locale independent format for dates in SQL statements Pyrrho maintains this with locale neutral database files From this viewpoint localisation is a matter for client configuration since once dates currency amounts etc are being displayed in the client the client application will use the Ul properties set in the client s operating system Some areas of localisation are notorious no two people in Scotland will agree on how to sort the names Mabon Mackay MacKay McKay Macdonald McDonald MacDonald M Donald Martin and the placement of names starting with de or the treatment of double surnames in Spain present well known problems The Unicode reports http www unicode org reports tr10 give examples including conventions for orderings based on accents whether case is considered or punctuation or combination characters 78 The Pyrrho Book May 2015 Fortunately the makers of operating systems have solved these problems for us with satisfactory libraries to associate acceptable behaviours with a given locale While the result will not please everyone at least it will be consistent across a large number of applications written for that operating system Thus ordering of stri
125. QL timestamp data type RdfDateTime The iri defined version of this Interval The SQL Interval type Collection The SQL array type Multiset The SQL multiset type UnionNumeric A union data type for constants that can be coerced to numeric or real UnionDate A union of Date Timespan Timestamp Interval for constants 38 The Pyrrho Book May 2015 Chapter 4 Database Servers In this chapter we look at the architecture of a database service from the viewpoint of the communication between client and server We will consider some alternative architectures along the way 4 1 Servers and services The usual model of computing is that a great many processes programs are running on any computer at any time Under Windows or Linux around 50 processes have started up by the time you log in These are almost all services some are part of the operating system and some are separate executables called servers in Windows the boundary is often blurred since DLLs are called operating system extensions Separate services are set up when something needs to be shared between processes between users on a multi user system or between tasks where several are running at the same time What is shared might be e aresource such as a printer e adata file e acommunication gateway so that messages to or from different tasks on the computer don t get jumbled up Some resources such as the processor memory devices are shared directly inside
126. S c 2015 Malcolm Crowe and UniverPyrrho DBMS c 2015 Malcolm Crowe and connection 1 File 5 2 19 March 2015 www pyrrhodb com 5 2 19 March 2015 www pyrrhodb com 1 Protocol byte ExecuteReader PyrrhoDBMS protocol on 127 0 0 1 34 Connecting D 3 127 0 0 1 5434 DbStorage F1 complete for C _ osp len 39 Database folde A About to Begin D 3 Enter to Continue Coordinating Commit for tid 2 Connection 2 Coordinator 127 0 0 1 5435 FiledClosed D 3 Enter to Continue Ficus 2 Protocol byte RemoteBegin PyrrhoDBMS protocol on 127 0 0 1 5435 Phase 1 for 8 Enter to start 2 Protocol byte CloseConnection Database folder B Praca ah for ota Enter to Tart Exception 00000 Connection 2 Coordinator 127 0 0 1 5434pha5se 2 for 8 Enter to start 2 Rollback Connecting D 5 127 0 1 34 Phase 3 for mc Enter to start 2 Ends with 9 About to Begin D 5 Enter to Continue lstartcCommit for osp at 34 Connection 4 Coordinator 127 0 0 1 5435 Fileg 2 Protocol byte RemoteBegin DbStorage Flush complete for WC osp len 979 4 Protocol byte RemoteBegin 2 Protocol byte Fetch Phase 4 4 Enter to start 2 Protocol byte Fetch 3 tid 2 Committed Connection 4 Coordinator 127 0 0 1 543dConnecting D 5 127 0 0 1 5435 PyrrhoDBMS protocol on 127 0 0 1 5436 atabase folder C About to Begin D 5 Enter to Continue Connecting _ 127 0 0 1 5435 6 127 0 About to Begin 127 0 0 1 5435 6 Ent EM Command Prompt PyrrhoCmd p 5436 _ Fie f
127. S style or script If the table s string metadata begins with lt it should be an XSL transform and Pyrrho will generate and then transform the return data as XML AddPeriodColumnList ADD COLUMN Start_ColumnDefinition ADD COLUMN End_ColumnDefinition Create CREATE ROLE id Description_string CREATE DOMAIN id AS DomainDefinition CREATE FUNCTION id Parameters RETURNS Type Statement CREATE ORDERING FOR UDType_id EQUALS ONLY ORDER FULL BY Ordering CREATE PROCEDURE id Parameters Statement CREATE Method Statement CREATE TABLE id TableContents UriType Metadata 184 The Pyrrho Book May 2015 CREATE TRIGGER id BEFORE AFTER Event ON id RefObj Trigger CREATE TYPE id UNDER id AS Representation Method Method CREATE ViewDefinition CREATE XMLNAMESPACES XMLNDec XMLNDec CREATE INDEX Table_id Name_id UNIQUE Cols Metadata Method bodies in SQL2011 are specified by CREATE METHOD once the type has been created In Pyrrho types UNDER or Representation must be specified not both CREATE XMLNAMESPACES is for creating a persistent association of namespace uris with identifiers Representation StandardType Table_id Member Member UriType CheckConstraint UriType Abbrev_id 44 Namespace_id id uri Syntax with UriType is a Pyrrho extension Abbrev_id can only be supplied within a CREATE DOMAIN statement
128. SET id Collate National and varying are ignored and the names are regarded as equivalent in Pyrrho Collate COLLATE id There is no need to specify COLLATE UNICODE since this is the default collation COLLATE UCS_BASIC is supported but deprecated For the list of available collations see NET documentation FloatType FLOAT REAL DOUBLE PRECISION int int The names here are regarded as equivalent in Pyrrho IntegerType INT INTEGER BIGINT SMALLINT All these integer types are regarded as equivalent in Pyrrho LobType NATIONAL CHARACTER BINARY LARGE OBJECT BLOB CLOB NCLOB National is ignored the character large object types are regarded as equivalent to CHAR since they represent unbounded character strings and of course BINARY LARGE OBJECT is the same as BLOB 188 The Pyrrho Book May 2015 NumericType NUMERIC DECIMAL DEC int int The names here are regarded as equivalent in Pyrrho DateTimeType DATE TIME TIMESTAMP IntervalField TO IntervalField int The use of IntervalFields when declaring DateTimeType is an addition to the SQL standard IntervalType INTERVAL IntervalField TO IntervalField IntervalField YEAR MONTH DAY HOUR MINUTE SECOND int DefinedType ROW TABLE Representation Type ARRAY Type MULTISET The TABLE alternative here is a Pyrrho extension to SQ
129. Selectltem Value AS id id id TableExpression FromClause WhereClause GroupByClause HavingClause WindowClause 189 The Pyrrho Book May 2015 GroupByClause and HavingClause are used with aggregate functions FromClause FROM TableReference TableReference WhereClause WHERE BooleanExpr GroupByClause GROUP BY DISTINCT ALL GroupingSet GroupingSet GroupingSet OrdinaryGroup RollCube GroupingSpec OrdinaryGroup ColumnRef Collate f ColumnRef Collate ColumnRef Collate RollCube ROLLUP CUBE OrdinaryGroup OrdinaryGroup GroupingSpec GROUPING SETS GroupingSet GroupingSet HavingClause HAVING BooleanExpr WindowClause WINDOW WindowDef WindowDef Window clauses are only useful with window functions which are discussed in section A6 7 WindowDef id AS WindowDetails WindowDetails Window_id PartitionClause OrderByClause WindowFrame PartitionClause PARTITION BY OrdinaryGroup WindowFrame ROWS RANGE WindowStart WindowBetween Exclusion WindowStart Value UNBOUNDED PRECEDING CURRENT ROW WindowBetween BETWEEN WindowBound AND WindowBound WindowBound WindowStart Value UNBOUNDED FOLLOWING Exclusion EXCLUDE CURRENT ROW GROUP TIES NO OTHERS TableReference Ta
130. System Linq using System Text using Pyrrho namespace ConsoleApplicationl Summary Class Person from Database home Role home summary public class Person public System Int64 Id primary key public System String Name public System String City public System Int64 Age Summary Class Thing from Database home Role home summary public class Thing f public System Int64 Id primary key public Person Owner public System Int64 Cost public System String Descr class Program static void Main string args Data source PyrrhoConnect db new PyrrhoConnect Files home db Open constructs an index for looking up t Owner as a side effect var people new PyrrhoTable lt Person gt db var things new PyrrhoTable lt Thing gt db Query creation 30 The Pyrrho Book May 2015 var queryl from t in things where t Cost gt 300 select new t Owner Name t Cost Query execution foreach var t in queryl Console WriteLine t ToString var query2 from p in people select new p Name Things from t in things where t Owner Id p Id select t foreach var t in query2 Console WriteLine t Name foreach var u in t Things Console WriteLine u Descr db Close 3 7 Documents Databases outlast hardware and software platforms Many legacy database systems still are in use today after 50 years Databases need to be designed for
131. T string 5 Compensation mechanisms should be supported by the DBMS if required by business logic But they should not be introduced merely because the DBMS does not support Web applications or transactions properly Pyrrho offers row version checking and other forensic methods to explore the dependency of later events on particular transactions but the use in the literature of phrases such as automatic compensation merely indicates poor transaction design or support 17 The Pyrrho Book May 2015 var rdr cmd ExecuteReader while rdr Read access the returned data using rdr 0 rdr 1 rdr Close conn Close This coding pattern is used for SQL strings that do SELECT You can use cmd ExecuteNonQuery for other sorts of SQL commands update delete etc You can only have one active data reader per connection you can close one and start another of course You can have more than one Connection but remember that the DBMS will treat the two connections as completely separate so that the transaction mechanisms may mean that the two connections see the same or different data For this reason if we need to traverse data from several tables together we should use SQL joins this should save a lot of work anyway We generally keep connections open for as little time as possible as they can consume resources on the server PHP starts the same way Sconn new COM connectionObject Sc
132. Text select from Member var rdr cmd ExecuteReader Members Children Clear var nr while rdr Read var rd new RowDefinition rd Height new Gridlength 1 GridUnitType Auto Members RowDefinitions Add rd for int j j lt 3 j AddBox rdr nr j nr void AddBox IDataReader r int nr int nc var tx new TextBox tx Text r nc ToString Mamban Childnnn AdAlts e A1 4 Using SQL Server Express Using SQL Server Ce resembles using SQL Server in many ways much of the interface in Visual Studio and for programming is the same But the two systems differ much more than their name suggests Either of the two previous exercises can be carried out with SQL Server and the instructions for creating the database with Visual Studio contain many of the same steps 1 First create the database we want on the server In Server Explorer right click Data Connectons and select Add Connection If prompted select Microsoft SQL Server Give the Server name as SQLEXPRESS and the database name as Club Confirm that you want to create the database View Server Explorer and expand the connection to the new database right click Tables and select Create Table Add the columns we want and set the Primary Key Click Save and In the New Table dialogue give the table name as Member Similarly create the Played table Create the foreign key references by right clicking the Winner column and selectin
133. The Pyrrho Book Malcolm Crowe University of the West of Scotland www pyrrhodb com ISBN 978 1 903978 50 4 O 2015 University of the West of Scotland Paisley University of the West of Scotland 2015 The Pyrrho Book May 2015 Contents Chapter 1 Introduction to the Book ccssccssssccssssscssssccsssccssssscsssscssssssssesssssseccsssssseseaees 7 11 Download Pyr 0 A A A ea s 8 2 The Py DBMS SiS E ac RSS 9 a A AS 9 lA Database A ON 10 A O 10 LOCA EU ed 10 THe SQOLAPTOMPt i a a e SS 11 Chapter 2 Data Consistency Transparency and Durability oooooooooooooo 14 E e a chide E a E iment dai 15 A A 16 AE K LE BLOA AES A EE E E E A EEE EE EE E 16 2 4 Tra isactionS nispi e EE EEE N A TE E e canica 16 2 5 Application programming interfaces ADO NET oooooccnnccconcnnonnconncnoncnnnnnonnccnnncnonccnnnos 17 2 6 A first benchmark mesos aia tired supadeoanedaaians 18 21 Pyrrho s internal struct anton 19 Key features of Pyrrho s de ds 21 Chapter 3 Database Desierto reinar arenas 24 3 1 CORA ltd 24 Example L database dis 24 3 2 Pyrrho s logs and system tables titi oi 25 Example 26 apple O E E Oe a 26 DEV HG JAY B DoI E 1 E E E EE E EEE OS 28 JI Ledo cul 29 A O ts lao 30 A A 31 E neers 32 3 8 Pyrrho DBMS low level desit n ir nee eei a a a 32 BTS cai ciao 33 A E E E a ae EEEE ea E 34 SlotEntmerator KEA A E E ti 34 ATree lt K Vi Subclasses ives E dia 35 tegira hene a saws Casta aa a t a a iaa 35 DG Cita ns
134. The transmission and recovery of Pyrrhonism American Philological Association 2002 ISBN 0195146719 Fonseca J Vieira M Madeira H 2008 Online Detection of Malicious Data Access using DBMS Auditing Proceedings of the 2008 ACM symposium on Applied Computing Fortaleza Brazil p 1013 1020 Frank L 2011 Architecture for Integrating Heterogeneous Distributed Databases Using Supplier Integrated E Commerce Systems as an Example Computer and Management CAMAN 2011 International Conference on pp 1 4 19 21 May 2011 doi 10 1109 CAMAN 2011 5778783 Garus K 2012 Version Based Optimistic Concurrency Control in JPA Hibernate Haritsa J R Carey M J Livny M 1990 December Dynamic real time optimistic concurrency control In Real Time Systems Symposium 1990 Proceedings 11th pp 94 103 IEEE IBM 2011 SolidDB v7 0 announcement http www 01 ibm com common ssi rep ca 1 897 ENUS211 491 ENUS211 491 PDF lyer S 2009 New approaches to securing the database Network Security Volume 2009 Issue 11 November 2009 Pages 4 8 ISSN 1353 4858 10 1016 51353 4858 09 70120 5 93 The Pyrrho Book May 2015 Kaspi S Venkataraman S 2014 Performance Analysis of Concurrency Control Mechamisms for OLTP Databases International Joiurnal of Information and Education Technology 4 p 313 318 Kung H T Robinson J T 1981 On optimistic methods of concurrency control ACM Transactions of Database Sty
135. ad only copies of tables some may control transactions of some data held locally etc 9 1 Distributed transactions Pyrrho like other DBMSs supports many aspects of such distributed database configuration and naturally is extremely strict about preserving ACID properties even for distributed databases Provided clients always access the same database server all the guarantees from Chapter 3 and the associated analysis hold good Unlike most other DBMSs Pyrrho has many fewer issues over database locking Transactions that change data managed by more than one transaction master will take longer as a version of three phase commit is required but the database remains accessible snapshot isolation while this is going on Unfortunately however the durability of the changes now depends on the survival of more than one durable storage installation If a disaster occurs then any copy of a physical database file can be used to restore the service as of the date the copy was made but it is possible for copies of different parts of a distributed database not to be fully in synch if this happens For this reason Pyrrho records all distributed transactions in a special way in the log so that if a database is cold started a rare occurrence in production environments it checks every participant in distributed transactions to ensure that all the records agree If a fully ACID database is widely copied and distributed we will easily find consistent
136. ad method give the code as follows var cmd conn CreateCommand cmd CommandText select from members var rdr cmd ExecuteReader dataGridView1 ColumnCount rdr FieldCount dataGridView1 ColumnHeadersVisible true for int j 0 j lt rdr FieldCount j dataGridView1 Columns j Name rdr GetName j while rdr Read var row new string rdr FieldCount for int j 0 j lt rdr FieldCount j row j rdr j ToString dataGridView1 Rows Add row 103 The Pyrrho Book May 2015 t clubOSP Form1 using System Ling using System Text using System Windows Forms using Pyrrho Q dataGridView1_RowValidated object sender DataGridViewCellEventArgs e Elnamespace clubOsP E public partial class Forml Form t PyrrhoConnect conn E public Form1 _ SURNAME Bloggs conn new PyrrhoConnect Files club Black conn Open InitializeComponent E private void Forml_Load object sender EventArgs e G var cmd conn CreateCommand cmd CommandText select from members var rdr cmd ExecuteReader dataGridViewl ColumnCount rdr FieldCount dataGridViewl ColumnHeadersVisible true for int j 0 j lt rdr FieldCount j dataGridView1 Columns j Name rdr GetName j while rdr Read var row new string rdr FieldCount for int j j lt rdr FieldCount j row j rdr j ToString dataGridView1 Rows Add row I ww Stop
137. ain details of when and by whom entries were made in the database 54 The Pyrrho Book May 2015 Secondly Pyrrho supports a sort of time travel in which a Stop time can be specified in the connection string see chapter 6 The connection then allows the database to be seen exactly as it was at that time and provided the operating system can restore the right user identities and application versions these can be used to inspect the database which is generally easier than working with the log files In complex cases a detailed investigation of the database as it was at a former time may be necessary to discover just how a particular user and role could have made a particular change to the database since the change might have been made indirectly for example by a trigger or a stored procedure One extension to SQL2011 syntax which assists with forensic investigation is the pseudo table ROWS n where n is the Pos attribute of the table concerned in SysSTable see Appendix 8 For example suppose we want a complete history of all insert update and delete operations on table BOOK Then lookup BOOK in SysSTable select Pos from SysSTable where Name BOOK If this yields 274 then the required history is select from rows 274 These can of course be combined select from rows select Pos from SysSTable where Name BOOK The second set of parentheses is needed in SQL2011 here to force a scalar subquery r
138. alisation D 127 0 0 1 5434 11 Enter to Col 12 Ends with 9 2 for D 11 Enter to start Connection 14 Coordinator 127 0 0 1 5436 to Request D 127 0 0 1 5434 11 Enter to Continue Connecting D 17 127 0 0 1 5434 3 for D 11 Enter to start About to Begin D 17 Enter to Continue to Commit D 127 0 0 1 5434 11 Enter to Continue 14 Protocol byte RemoteBegin Closed D 127 0 0 1 5434 11 Enter to Continue Connection 16 Coordinator 127 0 0 1 5436 Phase 4 for D 11 Enter to start Connecting D 19 127 0 0 1 5434 Connecting D 127 0 0 1 5434 11 127 0 0 1 5434 About to Begin D 19 Enter to Continue About to Begin D 127 0 1 5434 11 Enter to Continue 16 Protocol byte RemoteBegin Closed D 127 0 0 1 5434 11 Enter to Continue 16 Protocol byte GetMaster 5 tid 4 Committed Fil H hi View ary 7 a ome Share iew 1 into _ e 0 0 1 5436 2 a 2 student o DATA E A i a gt rhoCmd p Name E L osp D osp lt 2 items DATA E B A Name Date modified osp D osp 2 items su y T DATA E C Name Osp 156 The Pyrrho Book May 2015 At this precise point B is out of sync with A and this will be discovered next time anything connects to D on B In the PyrrhoCmd window let us check table E EN Command Prompt osp T p 5434 d A s 0 S 0 BH Command Prompt OSP T d B p 5435 s 0 S EM Command Prompt OSP T d 1C p 5436 s 0 S 0 M 0 27 0 0 1 5434 11
139. ally a client side library whose methods manage the low level communication with the server Since low level details will usually be platform dependent it is considered bad design for a client application to write directly to the communications stream Instead programming conventions have grown up for different sorts of service so that for example client libraries for database services all look very similar as we have seen in Labs 1 and 2 in this course In the early days of programming distributed systems a monolithic application would be simply broken into client and server by placing some of its components functions etc on the server side Application code on the client side would be unaffected because proxy functions were provided on the client side with the same names and parameters as before The proxy would marshal its parameters for transmission to the server This data would be disassembled on the server and used to cal the real server side function and so on Nowadays we try to design in client server design from the outset 4 5 Sessions As we have seen the lifetime of the connection is an important consideration the length of time connected to the server using PCT is called a TCP IP session For database services it often happens that very large amounts of data need to be transmitted between the client and the server involving many steps and client side decisions As we will see the whole notion of database transactions i
140. ance Exponential Extract Floor Grouping Last LengthExpression Maximum Minimum Modulus NaturalLogarithm Next Nullif Occurrences_Regex Percentile Position Position Regex PowerFunction Rank Regression RowNumber Schema SquareRoot StandardDeviation Sum Variance AbsoluteValue ABS Value Avg AVG DISTINCT ALL Value FuncOpt Ceiling CEIL CEILING Value Y Coalesce COALESCE Value Value Y Correlation CORR Value Value Y FuncOpt Count COUNT Y 194 The Pyrrho Book May 2015 COUNT DISTINCT ALL Value FuncOpt Covariance COVAR_POP COVAR_SAMP Value Value FuncOpt Exponential EXP Value Extract EXTRACT ExtractField FROM Value ExtractField YEAR MONTH DAY HOUR MINUTE SECOND Floor FLOOR Value Grouping GROUPING ColumnRef ColumnRef Last LAST ColumnRef OVER WindowSpec LengthExpression CHAR_LENGTH CHARACTER_LENGTH OCTET_LENGTH Value Maximum MAX DISTINCT ALL Value FuncOpt Minimum MIN DISTINCT ALL Value FuncOpt Modulus MOD Value Value NaturalLogarithm LN Value Next NEXT ColumnRef OVER WindowSpec Null
141. and Po Hd Dames lhis LE Load __ l erat MA Leioa Bilge Ex Te Hi Ti Dom Doe hora Hat Lip Lee Bora Falada Den 4 4 4 4 i i 218 ALTE E DAT Tra p Lita 4 4 i i 4 i t PE AME HE l TA Ip E f f 1 T T t T T T T I7 BEK 4D 7 MHI Tin eba Lis a t 1 Se EIE aL I DHEN Hipi ME Aar UMSE a h ae L Tea Lik kt D Go ETEA T Lpr Y Likes Pky BEE I uE ihr likes Era Hi Ce C Corrariira ic a i 1 Jit e a LA 07 bahir Eni rar F ae ititi iae Pes Tabir Hare a Tera Ti bieebil reari lipii Brilis Esteriro Enf mr Y t HI Ta Tn Les i ATEOA bd i CaA Fis Lieh D ESE dam p F PMI kame J a nhre a a Tee Tr J dg 7 x ta Paz Le BRD Add an Taas URH ince j i F k Ps pr f i 66 The Pyrrho Book May 2015 l Connachon Hear localhost fant MI Cutie Library table dera As expected we see the librarian s column names in the second two tables But the biggest difference is the way that the Default value for the ANAME or Author column is shown None of these exactly matches the actual definition used select name from author a where a id aid The first screenshot shows the identifiers capitalised the second uses the LIBRARIAN s name Authorid for the AID column and in the third the code cannot be displayed since the READER role does not know about the AUTHOR table In fact Pyrrho uses numeric identifiers internally select 158 from 68 a where a 119 277 and i
142. and the SQL2011 standard and thus are unlikely to be incorporated at any stage These include the DriverManager class the SQLPermission class PreparedStaments and their parameters DataSources and Savepoints The assumption is that clients open a Connection to a database and use Statements and ResultSets to manipulate the database On the other hand the intention is that entities specified as such in the database metadata should be retrievable using strongly typed generic client side methods with the help of reflection Specifically single entity short cuts from Connection will lead to generic versions of first and next that automatically populate the public fields of specified entity classes import org pyrrhodb Connection import java sql Statement import java sql ResultSet public class JCTest static Connection conn public static void main String args throws Exception conn Connection getConnection localhost def guest def 28 The Pyrrho Book May 2015 System out println rs getInt B rs getString C CreateTable ShowTable static void CreateTable throws Exception try conn act drop table a catch Exception e conn act create table a b int c char conn act insert into a values 1 One 2 Two static void ShowTable try Statement stmt conn createStatement ResultSet rs stmt executeQuery select from a for boolean b rs fi
143. ange LocalTransaction to D on A to A s LocalSlave proxy for the new Partition on B which is a Master and the remote configuration file The verification step requires B to tell A about the databases it already has A is examining B s indexes EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EM Command Prompt OSP T p 5435 d B s 0 S 0 M 0 1 for _ 11 Enter to start 1 5 for _ 11 Enter to start 2 for _ 11 Enter to start Phase 3 for _ 11 Enter to start IStartCommit for _ osp at 34 Coordi g Commit for DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 11 Enter to start 10 tid 8 Committed Connecting D2 13 127 0 0 1 5435 About to Begin D2 13 Enter to Continue onnecting _ 127 0 0 1 5435 14 127 0 0 1 5435 2 About to Begin _ 127 0 0 1 5435 14 Enter to Continypbs age Flush complete for 7 Coordinating Commit for tid 6 F for _ Enter to st Reconfigure _ i LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 5 Prot Phase 1 for _ 12 Enter to start L Mi la An x M Command Pramnt DurrhaCmd 5434 The next Enter on A send the Partition information from D to B for RePartition action EX Command Prompt OSP T p 5434 d A s 0 S 0 M 0 Command Prompt OSP T p 5435 d B s 0 S 0 M 0 hase 1 5 for _ 11 Enter to start Phase 2 for _ 11 Enter to start Phase 3 for _ 11 Enter to start IStartCommit for _ osp at 34 DbStorage Flush complete for A _ osp len
144. annot include generated column Grant of update column is not updatable Invalid transaction termination Incorrect Pyrrho connection or security violation This server disallows database creation by Database is read only Invalid user for database This operation requires a single database session Stop time was specified so database is read only Invalid role for database DataType requires database which is not connected User can access no columns of table Local and remote tables cannot be mixed in a query subqueries are ok DataType cannot be exported to database Connection is not open A reader is already open Unexpected reply Bad data type internal Stream closed Internal error Connection failed Badly formatted connection string Unexpected element in connection string Pyrrho service on at port not available or not reachable Feature 0 is not available in this edition of Pyrrho Database is loading Please try later Unsupported configuration operation Schema changes must be on base database Overlapping partitions Configuration update can only be for local server This server does not provide a Query service for Index is incompatible with the partitioning scheme Schema and data changes cannot be mixed in a partitioned transaction The calling assembly does not have type Type doesn t have a default constructor Type doesn t define field Types and do not matc
145. ar record are chained in a linked list and SQL Server may need to follow several pointers in a list to reach the right version Version records need to be kept in the version store only as long as there are there are operations that might require them 5 7 Transaction Profiling In the current literature transaction profiling is usually associated with detection of security breaches a transaction that does not fit any known business process deserves investigation This paper presents a new model for lightweight transaction profiling that also focuses on traffic optimisation by considering failed transactions also Where transactions repeatedly fail because of lock timeout or transaction conflict there are two options redesign of the task or scheduling it to take place during maintenance periods In experiments the mechanisms proposed here added less than 10 to DBMS memory usage and had no appreciable effect on transaction timings These mechanisms can bring immediate benefits in database security and can assist in improvements to access control and role management for a live system 48 The Pyrrho Book May 2015 The creation of transaction profiles is very important for proactive security monitoring and for database traffic management A poorly designed database or careless application design can lead to transactions that lock more data than they need to and thus degrade performance of the whole system Where transactions repeatedly fail
146. ared nothing replication From October 2010 Pyrrho supports this architecture Configuration files are used to specify the relationship between databases partition files and the partitioning mechanism see section 10 3 Since Pyrrho retains a historical record of the database creation of a new partition is an event in this history Each partition has its own database file The complete database consists of a collection of database files one of which the root has the same name as the database All of the files agree on the initial part of the file and effectively the collection of files form a branching tree like structure Each new partition starts out as a copy of a database file in the set and a configuration file entry is added to specify its file name the name of the base file it branches from and the new partition key data for the table s it contains Pyrrho servers only maintain indexes for the partition they have loaded and so a cold start is required for the base file server s No data is shared between partitions e g lookup tables will generally remain in the root file apart from information contained in the logs When supplying the connection string for a partitioned database the client must specify all of the database file partitions it wishes to connect to A client can obtain this set dynamically from the root database see section 8 1 8 A connection that needs to refer only to the data in a single parti
147. arts to the transaction it is coordinating Reconfigure the LocalSlave for D and a ProxyTransaction to make the configuration changes on A In A s server window we can see that B has already used the ProxyTransaction to check the contents of A s configuration database and finds it contains nothing conflicting with what is proposed In B s window press Enter twice 4 Protocol byte Fetch connection 6 Coordinator 127 0 DbStorage Flush complete for A _ 8 Coordinating Commit for tid 5 Reconfigure Phase 1 for _ 8 Enter to start ush f osp len 979 Phase 1 5 for _ 8 Enter to start Phase 2 for _ 8 Enter to start Phase 3 for _ 8 Enter to start StartCommit for _ DbStorage Flush complete for A _ osp len 5 Phase 4 for _ 8 Enter to start n 127 x Continue 8 tid 5 Committed 1 mmit for ti 6 Protocol byte RemoteBegin 6 Protocol byte IndexLookup 6 Protocol byte IndexNext P r ion _ 12 6 Protocol byte IndexLookup P Enter to 6 Protocol byte IndexNext ha 7 Enter to star A e D 5 Enter to Continue Blela x EM Command Prompt PyrrhoCmd p 5435 _ Home Share View t E DATA E A word 127 0 0 1 5434 Student L osp LJ D osp lt 2 items a Bs z x lt t E DATA E B ate modif 0sp 23 03 2015 15 0 B has no changes to make to database D so it is closed Press Enter twice 136 The Pyrrho Book May 2015 EN Com
148. as no longer relevant this amounts to a guarantee that all related information has been deleted from all remaining databases and prevents the verification of distributed transaction histories for this data 10 4 Partition sequences In some applications such as messaging records can be safely discarded once they have been processed Pyrrho is not immediately suitable for such data because transaction logs maintain a permanent record However the database partitioning concept can be used to achieve the same effect as follows Let a base database partition define the table s used for messaging and let these tables include a non null date field Then let ranges of dates define a new partition for these tables The configuration file needs to specify the partitions currently in use these can extend into the past and the future as may be convenient An application adding a message only needs to connect to the current partition An application accessing a message simply accesses the partition the message is in Messages can be deleted once they have been processed It is an optimised query to determine if a partition no longer contains any messages this partition file can be deleted and the corresponding entry marked as no longer relevant in the configuration 10 5 Managing Partitions Database partition management is a transacted process When the partition information changes this probably involves multiple rows in the _ Partition table of the
149. as reasonable However standard DBMS generally use fixed size data fields while Pyrrho does not and in 2013 20GB of memory no longer seems such a large amount Pyrrho s approach works best where durability is important such as customer records or financial transactions where data might need to be retrieved years later There are circumstances where durability may be less important for example in an enterprise service bus implementation where the horizon for durability is measured in minutes rather than years In ESB systems such messages would normally only be captured for permanent storage as part of a special troubleshooting activity 4 This design decision in Pyrrho is discussed further in section 3 7 15 The Pyrrho Book May 2015 2 2 Transparency Transparency or accountability means we should be able to discover why and when data changes who or what made the change was it routine or unusual In this course we will see this is closely tied to the concept of business roles What becomes important is not just who made the change but also what role they were playing e g lyer 2009 Oh and Park 2003 were they carrying out part of their day to day role of sales clerk or were they doing something else Some managers may be authorised to play more than one role but if they are carrying out a standard procedure it is reasonable for them to say what it is and not just arbitrary unaccountable caprice A good database design w
150. ase that gives the server details If the PartitionServer field is null the partition is marked as dropped The partition user and password are for server server access from the base database the base server password is a security precaution it must match the base server s account The PartName field enables a number of tableparts to be specified as being in the partition each part can specify a number of column conditions 84 The Pyrrho Book May 2015 Remember that _ is for distributed configuration information and is not affected by connection specific things such as creating or accessing non configured databases The current server s serverRole for non configured databases will be 7 local and O remote but they are not entered in the configuration tables No server is obliged to have complete information In the _ Database table Remote is null if ServerRole has bit 1 Master and otherwise references cause distributed transactions e g a server providing query and or storage only will usually list the master server as remote If no master server is configured the database is read only this is not an error However at most one server can have the master role To change configuration information the owner of the server account simply connects to the local _ database and modifies it The information about other servers is read only although selects joins etc show the overall information to the extent required for server serve
151. ataSource SQLEXPRESS Initial Catalog Club Integrated Security True A1 5 Using PyrrhoDB At one time Pyrrho also had DataAdapters but now it stays with the simple ADO NET approach so as to be more compatible with Linux So for the final exercise in this lab let us go back to Windows Forms but avoid DataAdapters am making a version of Pyrrho 5 1 available for the course and this should be available on the D drive of the virtual machines Copy the OSP folder to the C drive downloaded Open Source Pyrrho version 4 8 from www pyrrhodb com and extracted the files to C Temp created shortcuts on the desktop for the OSP application in C Temp OSP48 OSP and started up the server by right clicking the OSP shortcut and selecting Run as Administrator If prompted download NET 3 5 and reboot Leave the OSP window running To create the database use the command line tool PyrrhoCmd in C Temp OSP48 OSP Start a new ordinary Command Prompt window and change directory to cd Temp OSP48 OSP PyrrhoCmd club At the SQL gt prompt issue the following commands create table members id int primary key firstame char surname char insert into members values 56 Fred Bloggs insert into members values 78 Mary Black create table played id int primary key playedon date winner int references members loser int references members agreed boolean insert into played values 32 date 2014 01 09 56 78 false You can ver
152. atabase A initialises the configuration file in a transaction that it is coordinating connection 7 and at this point we need to use the Enter key five times in A s window to move things along 134 The Pyrrho Book May 2015 mit for ti H DATA E A Osp D osp lt iter es 7 DATA E B Osp EN Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 PyrrhoDBMS p 1 on 127 0 0 1 54 osp len for B _ o Enter to start ting D t to Begin D Connectin table E F int rt into sp len 979 4 password 127 0 0 1 5434 Student As before and the end of phase of the configuration initialisation transaction on connection 7 we see the empty configuration database has 979 bytes Home Share View E DATA E A 0sp D osp lt 2 items Ds O DATA E B Osp 2 2 atabase folder ction 1 tocol byte E ge Flush complete for B 3 Coordinating Commit for tic R fi 4 Ente 4 Ente 4 Enter to start mmitted 5 127 0 0 1 5 e table E F int prima t into E values 4 7 _ osp len 979 ontinue 27 0 0 1 5434 6 Enter to Continue ry key password The distributed transaction is coordinated by server B and so the current transaction needs to have references to the remote database that will b
153. base server operates on many database files on behalf of many clients A single client application can operate many databases at once by opening connections to one or more databases at a time The database file begins with a four byte magic cookie and ends with a five byte end of file marker that contains an encrypted digest of the database file This marker is a sort of digital signature placed there by the Pyrrho DBMS server intended to ensure that changes to the database are only made by 19 The Pyrrho Book May 2015 legitimate accountable DBMS operations that form part of the transaction record There are very few differences between the open source and professional editions of Pyrrho but the algorithm for the digest is one of them If the digest does not match the contents of the database file Pyrrho refuses to proceed and reports that the database is corrupt The first two records after the four byte marker record the owning role and owning user of the database All subsequent records in the transaction log record the role and user for the transaction together with a universal time timestamp All transaction records are immutable and can be referred to using their position in the data file which cannot be changed The maximum size of the database file is Ox40000000 but big data files are broken into 8GB sections for ease of management The data formats used for these transaction records are fully described in the Pyrrho manual
154. bases where writing to durable media does not matter In chapter 6 we will spend some time looking at information security issues In client server systems it must be assumed that authentication is dealt with at the time that connection to the server is established Secure protocols such as HTTPS can help with this Many databases are designed for use by people playing different roles bank managers bank tellers etc These roles could be separated out completely by the client applications but in this course we will study how good database design can help with maintaining a more secure system Database objects can have permissions associated with them for access by people in different roles and users can be authorised to exercise roles at different times 42 The Pyrrho Book May 2015 Chapter 5 Locking vs Optimistic Transactions In this chapter we return to the question of transaction control as a way of ensuring data consistency in multi user databases Although all commercial relational RDMS products use only pessimistic concurrency control there is a long tradition of research that optimistic concurrency provides a better solution e g Menasc and Nakamishi 1980 Haritsa et al 1990 Kaspi and Venkataraman 2014 The biggest conceptual hurdle in developing applications for Pyrrho is the use of optimistic transactions It is very important for programmers to accept this approach as a fact of life explained in the following paragraphs and n
155. be specified This precision is taken from the domain definition for the field if specified or is 13 bytes by default i e the default precision provides for a mantissa of up to 27 1 Character Data All character data is stored in the database in Unicode UTF8 culture neutral format Domains and character manipulation in SQL can specify a culture and string operations in the DBMS then conform to the culture specified for the particular operation The NET library provides a very good implementation of the requirements here and is used in the DBMS Unfortunately NET handles Normalization a bit differently from SQL2011 so there are five low level SQL functions whose implementation is problematic Documents From v 5 1 Pyrrho includes an implementation of Documents as in MongoDB Assignment of documents follows the MongoDB prescriptions where S operators determine how new data is combined into the existing document The same mechanism is implemented for Update records in the database so Document fields in Update records normally contain these operators and Pyrrho computes and caches the updated document when the Update is installed in the database Document comparison is implemented as matching fields this means that fields are ignored in the comparison unless they are in both documents the Sexists operator modifies this behaviour This simple mechanism can be combined with a partitioning scheme so that a simple SELECT statement
156. best results always ensure that all packets used on a channel have the same size This simple trick can affect communication speeds by a factor of 1000 Pyrrho always uses a packet size of 2048 octets For client server communications it is often important to use asynchronous I O calls This is extremely important for interactive applications you don t want the user s display to freeze while the process wits for a reply from a remote server Many programming systems such as Windows Forms already ensure that the interactive events are done by a separate thread but this brings its own complications and the run time system will insist on cross thread method invocation Invoke where required The messages on this two way communication channel are called application protocol data units PDU For example if your sporting club was not using SQL you might have messages for enrolling a new member for recording a match for a score etc The start of the message might have an identifier to say which message it is using a small integer 1 2 3 for the different actions and a set of strings for the different data involved If you were using SQL each request might just be a string consisting of an SQL statement e g insert into members This assumes that authentication of the user was already done during the connection step 4 4 The client library Since a service is designed to be used by a number of different applications there is usu
157. bleFactor Alias JoinedTable TableFactor Table_id FOR SYSTEM_TIME TimePeriodSpecification View_id ROWS int int Table_FunctionCall Subquery TableReference TABLE Value UNNEST Value XMLTABLE XMLOption xml PASSING NamedValue NamedValue XmIColumns STATIC Document_Value Document_Value T ROWS is a Pyrrho extension for table and cell logs and the last two options above are also Pyrrho specific static is for a single query that does not access a table and the other allows a specific list of documents to be supplied static is actually equaivalent to Alias AS id Cols 190 The Pyrrho Book May 2015 TimePeriodSpecification AS OF Value BETWEEN ASYMMETRIC SYMMETRIC Value AND Value FROM Value TO Value This syntax is slightly more general than in SQL2011 see section 5 2 3 Subquery QueryExpression Subqueries return different sorts of values depending on the context including simple values scalars structures arrays multisets etc rows and tables JoinedTable TableReference CROSS JOIN TableFactor TableReference NATURAL JoinType JOIN TableFactor TableReference JoinType JOIN TableFactor USING Cols TO Cols TableReference JoinType JOIN TableReference ON SearchCondition The TO part is an extension to named column joins for cases w
158. bringing a risk of inconsistency In the next section we explore the link between transactions and consistency and examine what this means for constraints Another difficult area for consistency is where some data is stored in one database or one computer and some elsewhere in a file in another database or on another computer In such situations it is best if responsibility for ensuring consistency resides somewhere for example with one of the DBMS involved but often there are real difficulties for example a transfer from one bank to another Recent research has revisited this problem addressing the impact of service oriented architectures e g Lars Frank 2011 We return to this sort of problem below 2 4 Transactions The practical way of ensuring consistency is to use transactions A transaction consists of a set of changes to the database that is logically ATOMIC That is although there might be more than one step the process comprising these steps is indivisible The classic example is that of a bank transfer Although there are two steps taking a sum of money from one account and placing it in another the process of transfer is logically indivisible During the process the total amount of money in the bank will be wrong So while the separate steps are proceeding nobody else should be able to see any of the changes until the process is complete and the data is consistent That is the transaction needs to be ISOLATED until it i
159. but possibly slightly out of date copies This might be totally satisfactory for our purposes We need to ensure only that we consistently use the same copy Accessing the transaction master might make a marginal improvement in the currency of the data but there may be a gigantic transaction about to be committed in the transaction master and isolation means you don t see the impending changes If we want to be sure our data is correct we can check with the transaction master by committing a read only transaction However the person who wants to do this should be warned that there is no guarantee that the data won t be changed immediately thereafter and before he can do what he plans to do next So it s better only to worry about such matters when actually making a change we read and then commit a change If the change works then the data on which it was based is still valid 83 The Pyrrho Book May 2015 With distributed transactions several transaction masters will be involved Since there is no locking the fact that the commit takes longer does not affect other readers but does delay the writer The transaction commit will only succeed when all the participants commit but then it is guaranteed durable The write is held up a bit but is then safe 9 2 Dynamic Configuration Each server has its own folder for holding databases although full pathnames can be specified for databases The configuration database if any is found in
160. byte ExecuteReader 11 8 Protocol byte RemoteBegin Connecting D 5 127 0 0 1 5435 col by elConnection 10 Coordinator 127 0 0 1 5436 Files D Modify tlabout to Begin D 5 Enter to Continue m 10 Connecting D 13 127 0 0 1 5434 Connecting D 9 127 0 0 1 5435 About to Begin D 13 Enter to Continue O Home Share View 1 DATA E A Name osp _ D osp We see another connection to A In B s window press Enter and similarly in C f Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S Bj Command Prompt OSP T d C p 5436 s 0 S 0 M 0 tartCommit for _ osp at 1137 Closed _ 127 0 0 1 5435 6 Enter to Continue i 4 Ends with 31 Phase 4 for D 7 Enter to start 6 Protocol byte CloseConnection Closed D 5 Enter to Continue i Phase 4 for _ 9 Enter to start 1 tid 1 Committed About to Close D 9 Enter to Continue 1 Ends with 1 Closed D 9 Enter to Continue Connection 5 Files D User asusrog Student 6 Ends with 9 5 Protocol byte ExecuteReader Connection 8 Coordinator 127 0 1 5436 Flconnecting D 5 127 0 0 1 5435 Connecting D 11 127 0 0 1 5434 About to Begin D 5 Enter to Continue About to Begin D 11 Enter to Continue Connecting D 9 127 0 0 1 5435 8 Protocol byte RemoteBegin About to Begin D 9 Enter to Continue Connection 10 Coordinator 127 0 0 1 5436 5 Protocol byte Data FilConnecting D 13 127 0 0 1 5434 5 Protocol byte Data About to Begin D
161. cked for records that conflict with the current transaction If conflicts are found the transaction rolls back In stage 2 the databases are locked and this check is repeated for even more recent records and if all is well the transaction is serialised to the data file Finally stage 3 the data just serialised is installed in the level 3 data structures and the locks are released Transactions that merely read data cannot conflict with any other transaction it is as if the entire transaction takes place at the begin time For transactions that make changes to the database 20 The Pyrrho Book May 2015 everything read by the transaction must still be valid at the time the transaction is committed so it is as if all of the steps of the transaction take place at the commit time From this account we see that even with optimistic concurrency there is always a short time when locks are applied but locking only occurs at the point of committing the transaction All of the transaction processing including constraint checking triggers etc takes place beforehand and all of the data required to commit the transaction has been assembled and is ready for serialisation Finally all of the above discussion needs to be understood in connection with Pyrrho s multi threading model Pyrrho DBMS uses multithreading at the level of connections level 4 each connection runs in a different thread The transaction mechanism described in the last cha
162. creation of table E with its initial two entries Close the session with C and examine the new partition now PyrrhoCmd p 5435 D2 table E table Logs Again we see both rows in the partitioned table but only one record in the partition 164 The Pyrrho Book May 2015 PRole 27 PUser Student PUser Transaction for 2 er 27 Time 30 03 2015 21 21 24 127 0 0 1 5434 974 127 0 0 1 5435 9 PTr C149 324 Record for 66 94 Record And in this log file we see the setting up of the partition D2 whose base is D a summary of the binary database schema for the partition provided by D and the single record that was copied across Note that both these events are in a single distributed transaction A5 5 From A insert some more records in E Again close the session with C Pyrrhocmd p 5434 D insert into E values 3 Three 2 Deux table E table Sys Table Check all four records show up in E when viewed from D on Aor D2 on B and verify from the logfiles that one new record each has been added to databases D and D2 The transaction is a distributed one here D 327 D2 345 165 The Pyrrho Book May 2015 EN Command Prompt PyrrhoCmd p 5435 D2 O x CH 2 SQL gt C E OSP gt PyrrhoCmd p 5435 D2 3 Three 127 PUser Student PUser 27 39 PTransaction for 2 Role 5 User 27 Time 30 03 2015 21 21 24 127 0 0 1 5434 974 127 0 0 1 5435 974 D 248 D2 39 PTransaction2 0 jo 111
163. ction will conflict with any A x such that description x is like y even if quantity x lt 40 Not all database experts consider that conflict arises here With PCC we can imagine that all rows of Products would be locked for the duration of C y transaction With OCC some implementations might not report any conflict on the grounds that C y does not modify quantities However as transactions A and B also compute a required payment for the items purchased the cost of the purchase might be debatable if transaction C was concurrently applying a discount On these grounds we would say that C y will conflict with any A x such that quantity x gt 100 Suppose Products contains an item 456 500 3x5 BOLT 101 3 00 and A 456 followed by C BOLT the cost of A is 3 00 and the Products table reads 456 500 3x5 BOLT 100 3 00 If C is followed by A the cost of A is 2 70 and the Products table contains 456 500 3x5 BOLT 100 2 70 The principle of serialisability of transactions should ensure that no other outcomes are possible In the absence of proper concurrency control both A and C might proceed on the basis of a snapshot of the Products table at the start of their transactions so that A would cost 3 00 and the Products table would have 456 500 3x5 BOLT 100 2 70 In this business scenario perhaps this uncertainty is unimportant but in scenarios such as control of dangerous industrial processes such uncertainties could be a mat
164. d databases that is situations where several physical databases act as a single one The database servers should handle all of the details so a database client should simply contact any of them with a query that can naively ignore the distribution issues The different physical databases might hold different tables or some tables might be partitioned vertically by columns or horizontally with some rows being held in different fragments or both For vertical partitioning the columns making up the primary key are usually common to all partitions For horizontal partitioning the fragments are usually based on elements of the primary key for example data from different countries might be in different partitions Data may also be replicated on multiple servers for increased availability Needless to say all such arrangements require significant management overhead by the DBMS so that a lot of care is needed to ensure that the benefits gained outweigh the costs It must be assumed that authentication is handled in some coordinated way so that all of the database servers can agree on who is allowed to access the data and what they are allowed to do Secondly the roles of the different servers must be established Some servers may simply act as agents forwarding requests to other servers and or combining the results from other servers some may process SQL queries against database tables held locally or on other servers some may provide re
165. d to the terminal window with the advice Enter to start up Type enter to start up the server EN Command Prompt OSP p 5434 d A s 0 S 0 M 0 SP p 5434 d A O 5 0 M ty of the West of Scotland folder We should see output from the OSP server announcing that it is using port 5434 and directory A as shown in the screenshot If the port or folder is wrong review the above setup and try again Leave this server running and the terminal window open Similarly in a different terminal window start up a server on port 5435 using folder B Leave this open also These windows will occasionally show diagnostic output as it is sometimes useful to know where a problem is first reported Command Prompt OSP p 5435 d B s 0 S 0 M 0 ta p 5435 d B s 5 0 M 0 o start up University of the West Now open two file browsers and change directory to the A and B folders We will use these window to check folder contents as we go along A5 2 Create a sample database on A In a third terminal window change to OSP and create database D on server A cd OSP PyrrhoCmd p 5434 D 160 The Pyrrho Book May 2015 File Home Share View 0 E t E DATA E gt A A Name is folder is empty The database does not appear in the folder until the first transaction to it is committed At the SQL gt prompt create a table E and then add some sample data create table E F int G char primary key F G
166. d using table references Such dependencies are tracked using the referers list so that updates to the referenced tables may be restricted for example where a column uses a domain a table uses a column a type uses a record structure defined by a table Changes to domain types therefore cascade through the in memory data structures at level 2 when a schema change is read from the physical media or prepared for serialisation This means that the Level 2 PhysBase has a default standardTypes structure that contains the names standard types with domaindefpos marked as undefined Obviously this ATree structure gets updated as standard types are reified in the PhysBase The SqlDataType structure also controls the fields columns of a structured type the supertypes under a data type has and the order function that is used It is possible to get hold of a SqlDataType for a record by using the DataTypeTracker information in the PhysBase This enables types with custom orderings to be used for primary keys since the indexes are constructed during database loading However the actual names of columns and types are not considered part of the SqlDataType they are role dependent so are generated at the session level For this reason types with the same name are not necessarily compatible and error messages try to give numeric references in addition to the names Because of custom orderings and role based naming at this level it is also possible to
167. declared fields or columns 79 The Pyrrho Book May 2015 fel PyrrhoCmd Create type int as x int y int Create e siz s Cw int h int Create 2 line as strt point en point gt Create type rect as tl point sz size constructor method rect xi int yl ink int y2 int method centre gt returns point Create table Figure id int primary key title char Create table FigureLineCid int primary key fig int references figure what SQL gt Create table FigureRect id int primary key fig int references figure what rect SQL gt create ructor method rect xi int yl int x2 int y2 int gt begin tl poin SZ 2etx2 x1 y2 y1 gt end gt method centre returns point for rect return point lt tl x sz w 2 tl function centrerect a int returns point return select what centrel igurerect where id a gt st into figure values i Diagram gt into figurerect values 1 1 rect point 1 2 gt size 3 4 gt gt gt into figurerect val 1 rect 4 5 6 7 gt gt rt into figureline values 1 line Ceontrersct ct centrerect 2 gt gt gt ble figureline LINECPOINTC2 4 gt POINT lt S 6 gt Note that the coordinates have been declared as int so the first point here is not 2 5 4 Arrays and multisets of known types do not need explicit type declaration Their use can be specified by the use of the keyword ARRAY or MULTISET following the type definition of a column or domain You can define ordering functions for any use
168. ded If someone accesses a partitioned table in the base database we should assume that they intend to access all of the partitions so we should extend the connection to all of the partitions 9 7 Transaction implementation Pyrrho s transaction design is actually very well suited to sharing cloud storage between database engines because its transaction serialisation handling is performed at the level of the binary records Physical s that are written to the durable storage when a transaction commits Pyrrho uses 87 The Pyrrho Book May 2015 optimistic locking which is also very well suited to use with cloud storage since it would be a bad idea to have an exclusive lock on the Cloud service For a proper understanding of the mechanism it is necessary first to mention that the tree and queue data structures managed in the Logical Database layer have the property that all their elements are immutable any change results in a new head structure and following links through new components of the data structure usually leads to components of the original structure So at the start of a transaction new headers for the database s involved are created which initially lead to the current committed state if a few transactions are in progress there will be several versions of the database s mostly coinciding on unchanged portions The changes associated with the transaction each have a Physical which will be written to durable st
169. dexNext CloseConnection m o a id ype E nai gear ia 5 E ES Validation of this transaction requires starting a two phase commit protocol with server A We begin with a Prepare which sends all of the proposed changes to server A Press Enter EX Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 DbStorage Flush complete for A _ osp len sp a Phase 4 for _ 8 Enter to start F ete osp len 979 8 tid 5 Committed y 6 Protocol byte RemoteBegin 6 Protocol byte IndexLookup 0 6 Protocol byte IndexNext bout t y Enter to Continue Protocol byte IndexLookup onnectir da 1 5434 6 127 0 0 1 5 Protocol byte IndexNext t to B n _ 127 1 Enter to Continue CloseConnection Coord ing Commit for tid 1 6 Protocol byte Prepare repare 2 physicals Ent sed D 5 Enter to Continue e 1 for _ 9 Enter to star t to P _6 f 6 Enter to Continue 1 5434 6 Enter Home Share View t E DATA E A 0 0 1 5435 4 127 0 0 1 5434 Student LJ osp LJ D osp lt 2 items B Be F x t E DATA E gt B 137 The Pyrrho Book May 2015 A receives the Prepare request containing two Records for _ From the above discussion we know that one of these is for Database and the other for _Client On B press Enter to perform the CheckSerialisation step this confirms no conflicting changes in A s configuration Command P
170. digital signature to guard against tampering with the database contents 21 The Pyrrho Book May 2015 22 Data structures in the higher levels of the database are frequently built from immutable elements For example if an entry in a list is to be changed what happens at the data structure level is that a replacement element for the list is constructed and a new list descriptor which accesses the modified data while the old list remains accessible from the old list descriptor In this way creating a local copy or snapshot of the database which occurs at the start of every transaction consists merely to making a new header for accessing the lists of database objects etc As the local transaction progresses this header will point to new headers for these lists as they are modified If the transaction aborts or is rolled back all of this data can be simply forgotten leaving the database unchanged With this design total separation of concurrent transactions is achieved and local transactions always see consistent states of the database When a local transaction commits however the database cannot simply be replaced by the local transaction object because other transactions may have been committed in the meantime If any of these changes conflict with data that this transaction has read read constraints or plans to modify transaction conflict then the transaction cannot be committed If there is no conflict the physical records pro
171. dows Forms Application in this folder called club 1 added a reference to Extensions gt MySQL Data and used the Toolbox to place a Data gt DataGridView in the Form1 window Ignore the prompt to Choose Data Source In Solution Explorer right click Form1 cs and choose View Code Add using MySql Data MySq lClient near the top and inside the public partial class add MySqlConnection conn null MySqlDataAdapter ad null 2 After InitializeComponent add using your user name and password var str server localhost database mydatabase userid root password MySQL_123 95 The Pyrrho Book May 2015 try gram cs amp Form1 Designer cs amp IAS Form cs Design club Form1 conn conn new using System Ling A F using System Text MySqlConnection str using System Threading Tasks A using System Windows Forms conn Open using MySql Data MySqlClient catch Exception ex Console WriteLine ex Message namespace club public partial class Forml Form i MySqlConnection conn null MySqlDataAdapter ad null Now we need to add two events to the public Form1 i program InitializeComponent var str server localhost database mydatabase userid Student password Paf w8rd 3 With the design view of o Form1 cs left click the form conn new MySqlConnection str eo conn Open then select the events tab in the Properties window and double catch Exception ex C
172. e Phase 3 for _ 12 Enter to start iStartCommit for _ osp at 974 DbStorage Flush complete for A _ osp len 1204 Phase 3 for D 13 Enter to start iStartCommit for D osp at 248 bStorage Flush complete for A D osp len 332 Phase 3 for D2 15 Enter to start About to Commit D2 13 Enter to Continue losed D2 13 Enter to Continue Phase 3 for _ 17 Enter to start About to Commit _ 127 0 0 1 5435 14 Enter to Continue losed _0127 0 0 1 5435 14 Enter to Continue osp len 1163 ase 4 for _ 12 Enter to start se 4 for D 13 Enter to start Bila X BE Command Prompt PyrrhoCmd p 5434 _ x rrhoCmd p QL gt create ta Home Share View t E DATA E gt A L osp D osp _ D _ 127 0 0 1 5434 974 _ 127 0 0 1 54 lt 3 items B D2 osp 0sp 30 03 2015 22 20 Command Prompt OSP T p 5434 d A s 0 S 0 M 0 XX 5 dA B s 0 5 0 M 0 About to Request D2 13 Enter to Continue Phase 2 for _ 17 Enter to start About to Request _ 127 0 0 435 14 Enter to Continue Phase 3 for _ 12 Enter to start IStartCommit for _ osp at 974 bStorage Flush complete for A _ osp len 1204 Phase 3 for D 13 Enter to start iStartCommit for D osp at 248 DbStorage Flush complete for A D osp len 332 Phase 3 for D2 15 Enter to start bout to Commit D2 13 Enter to Continue Closed D2 13 Enter to Continue Phase 3 for _ 17 Enter to start About to Commit _ 127 0 0 1 5435 14 E
173. e databases stored on the server but generally these system tables are for a single current database the RoleS tables give the properties as seen from the current role while the Log tables give access to the defining records All of these table are virtual in the sense that the contents are generated in this form only transiently and when required from the DBMS engine s internal data structures System Table Name Type of information SysSConnection Details of the current connection SysSHorizontal Horizontal partitioning information for partitions on the server SysSKnownRoles Databases Partitions and Roles available to the current user on this server SysSRole Roles available for the current database SysSRoleUser Authorised users for roles on the current database SysSServer A list of all servers known to this server SysS User A list of all users known in the current database RoleSClass Base tables key columns and C class definitions RoleSColumn Columns of base tables RoleSColumnCheck Column check constraints RoleSColumnPrivilege Role access privileges on table columns RoleSDomain Domain and type information accessible from the current role RoleSDomainCheck Domain check constraints RoleSIndex With standard SQL indexes are created to implement integrity and referential constraints RoleSIndexKey Key information for indexes RoleSMethod
174. e E F int primary key ISQL gt insert into E values 4 7 Share Home D DATA E A Name jso i rt into values D 127 0 0 1 5435 4 password 127 0 0 1 5434 Student m password Osp ISQL gt 2 items p m 142 The Pyrrho Book May 2015 In the final screenshot we can see in the file browser for folder A that the configuration database has been created on A Records will be added to both currently empty configuration databases when the distributed transaction commits The distributed transaction mechanism is quite an old part of the Pyrrho DBMS and for example is used when an application sets up a transaction using multiple databases so called multi database connections even on the same server It uses three phase commit which has been improved in version 5 0 to reach high standards of transaction safety As an exercise repeat all of the above steps in an explicit transaction and examine the distribute databas tables Database and _Client before committing the transaction You will find although nothing has yet been written to disk we see that the _ Database table contains the expected contents A4 7 What happened in step 6 At this point we have effectively reached the end of step 3 To get nearly the same screenshots as me restart the three servers still with the T flag with the Enter key used twice during B s startup sequence E Command Prompt osp T p 5434 d A s 0
175. e VirtBase class that also contains the new information that will be added if the transaction commits The above considerations lead to the following feature set for Pyrrho 1 Transaction commits correspond one to one to disk operations completion of a transaction is accompanied by a force write of a database record to the disk There is a 5 byte end of file marker which is overwritten by each new transaction but otherwise the physical records once written are immutable Deletion of records or database objects is a matter for the logical database not the physical database This makes the database fully auditable the records for each transaction can always be recovered along with details about the transaction the user the timestamp the role of the transaction 2 Because data is immutable once recorded the physical position of a record in the data file its defining position can be used to identify database objects and records for all future time as names can change Needless to say the current structure of the database object or the current values of a record may well depend on subsequent data which should be examined for relevant alterations and updates or even drops and deletes Pyrrho threads together the physical records that refer to the same defining position to facilitate backward searching in the database file and forward searching in the corresponding memory structures The end of file marker includes a kind of
176. e a e E 106 Appendix 2 The Transactions mystery tour cccssccccsssssscccssssscccsssescccsssssscsscssseceees 107 Appendix 3 Roles and SECUIICY sisccinrsesesesecsonsvonascenvosecesscostesssssnssdoedocscnessoesvadsonssnsetsoeoseney 119 Ao Ne The sportine UD A A A eeu edie eae ete 119 A3 2 A forensic investigation ia 120 A3 3 Some mo r PyrrhoDB stuff vesis sienen oris E RE 120 Appendix 4 The Distributed Database Tutorial for Windows e sesesseesessossesossossesossee 122 AAV Sart up THE SEUS nia 122 A4 2 Create a sample database musica iia 123 A4 3 Configure a storage replica of the sample database oooonncccnnonccinoncccnocccnnnnccnnnnnss 125 A4 4 Examining the configuration file oooococnnococinucccooncnononcnononcnononoconnnacnnnnacnnnnccnnnnnss 126 AA 5 What happened IW EP eo 127 A4 6 A distributed transaction DeGINS ee eeeececesececeeccecseeeeceeeeecsececseeeeseeeetaeeeeaees 134 AA TW hat happened 10 Step OI A eS 143 A4 8 Creating the query service for D on C ooococonoccconccocoonnnononcnononnncnnnncnnnnncnnnncnnnnnccnnnnoss 144 AAO What happened in SEPT la dise 151 Appendix 5 Partitioned Database Tutorial seseesoesessosoesossossesossossesossossossossesossossesossse 159 PO up the SERVES Ooo ee a GG Ess BN ae aie 159 A5 2 Create a sample database on A iii Aiea ded 160 A5 S BP ANiti EE 162 AS 4 Examine the database and PAIN A 163 AS 5 From A insert some more records in E
177. e created and modified The name of the database on A will of course be _ osp but this remote database is referred to in server Bas 127 0 0 1 5434 The name of both databases is _ so inside the server databases are catalogued by transName instead of name to keep such entries separate The current transaction on B configures information about a remote database called 127 0 0 1 5434 and adds it to the transaction 135 The Pyrrho Book May 2015 To this ProxyTransaction referring to _ on A it then adds the counterpart of the new recordin _ on B Unfortunately this is not a simple matter as we will first need to check what information the configuration file on A currently contains about D Server B is now ready to make the requested entries in the distributed configuration database In B s window press Enter EM Command Prompt osp T p 5434 d A s 0 S 0 M 0 BH Command Prompt OSP T d B p 5435 s 0 S 0 M 0 3 Protocol byte Fetch Connection 5 Coordinator 127 0 0 1 5435 Files _ Role User DbStorage Flush complete for A _ osp len 39 7 Coordinating Commit for tid 4 Reconfigure _ Phase 1 for _ 7 Enter to start DbStorage Flush complete for A _ osp len 979 Pr _ 7 Enter to start 7 tid 4 Committed 5 Protocol byte RemoteBegin 5 Protocol byte IndexLookup 5 Protocol byte IndexNext 5 Protocol byte IndexLookup 5 Protocol byte IndexNext a A i ar A eae B tells us that there are 3 p
178. e database file while it is operating 41 The Pyrrho Book May 2015 4 8 Alternative architectures Needless to say various alternatives to the above architectural description are possible On a personal computer sharing of data is less of an issue so for example MS Access is a database product that supports no sharing at all If such a database is on a shared folder whole file locking mechanisms exclusive access above are the best that can be managed Another no sharing possibility is where an application has an embedded database This is a persistent store in the application that is not accessible by any other application If the database actually uses database technology such as SQL then the application will include a database engine in its executable code In other cases the database technology is less important than the sharing and people share No SQL databases such a twitter feeds Such arrangements involve rapid non transacted publication of data and nobody minds too much if a tweet gets overwritten Since the data is not structured there are no indexes to keep in synchronisation with data and no database constraints Yet another sort of database is provided in big data warehousing where huge read only aggregations from data sources have been made accessible Typically these systems avoid trouble by disallowing updates to the warehoused data Finally at the ultra fast end of the spectrum we have in memory data
179. e echoed to the terminal window with the advice Enter to start up Use the enter key to start up the server Command Prompt OSP d A p 5434 s 0 S 0 M 0 E O X We should see output from the OSP server announcing that it is using port 5434 and directory Al as shown here Similarly in different command windows start up servers on ports 5435 and 5436 and folders B and C Leave these open also These windows will occasionally show diagnostic output as in the distributed system under development it is sometimes useful to know where a problem is first reported 122 The Pyrrho Book May 2015 EN Command Prompt osp p 5434 d A s 0 S 0 M i BN Command Prompt OSP d B p 5435 s 0 S 0 BN Command Prompt OSP d C p 5436 s 0 ps OSP gt OSP d C p 5436 s 0 S 0 M4 Enter to sti d C p 5436 s 5 0 M 0 Enter to lcolm Crowe and UsPyrrho DBMS c 2015 Malcolm Crowe anc 3 2 19 March 2015 www pyrrhodb com PyrrhoDBMS protocol on 127 0 0 1 5434 rrh 27 0 0 5 PyrrhoDBMS protocol on 127 0 0 1 5436 Database folder A o B Database folder C Bl lA A E Home Share View EN Command Prompt t E DATA E gt A This folder is empt 0 items B E DATA E B o nis folder is empty 0 items lac 7 In these screenshots have overlapped these windows and I have adjusted the properties so it is easier to see which window is which when show just one It is stil
180. eReader even though it is not a SELECT or TABLE command We are in auto commit mode so the commit of this transaction is already underway The server is telling us it first creatied an empty database D osp in folder A has started a LocalTransaction to check the proposed changes and is waiting for us to confirm Phase 1 transaction validation We press Enter in the server window several times until the Committed message appears 129 The Pyrrho Book May 2015 At this point we also see the SQL gt prompt in the PyrrhoCmd window We see that the changes were written to disk in Phase 3 EN Command Prompt osp T p 5434 d A s 0 S 0 M 0 J O T p 5434 d A s S M 0 Enter to start up yrrho DBMS c 2015 Malcolm Crowe and University of the West of Scotland 5 2 19 March 2015 www pyrrhodb com PyrrhoDBMS protocol on 127 0 0 1 5434 atabase folder MAN Connection 1 Files D User asusrog Student 1 Protocol byte ExecuteReader bStorage Flush complete for A D osp len 1 Coordinating Commit for tid 1 LocalTransaction D Phase 1 for D 4 Enter to start Phase 1 5 for D 4 Enter to start Phase 2 for D 4 Enter to start Phase 3 for D 4 Enter to start StartCommit for D osp at 50 bStorage Flush complete for A D osp len Phase 4 for D 4 Enter to start 1 tid 1 Committed EN Command Prompt PyrrhoCmd p 5434 D E OSP gt PyrrhoCmd p 5434 D SQL gt create table E F int primary key SQL gt Share Vi
181. econd within minute TIMEZONE_HOUR Hour value of time zone displacement TIMEZONE_MINUTE Minute value of time zone displacement There is an ordering of the significance of lt primary datetime field gt s This is from most significant to least significant YEAR MONTH DAY HOUR MINUTE and SECOND The lt primary datetime field gt s other than SECOND contain non negative integer values constrained by the natural rules for dates using the Gregorian calendar SECOND however can be defined to have a lt time fractional seconds precision gt that indicates the number of decimal digits maintained following the decimal point in the seconds value a non negative exact numeric value There are three classes of datetime data types defined within this part of ISO IEC 9075 e DATE contains the lt primary datetime field gt s YEAR MONTH and DAY e TIME contains the lt primary datetime field gt s HOUR MINUTE and SECOND e TIMESTAMP contains the lt primary datetime field gt s YEAR MONTH DAY HOUR MINUTE and SECOND Items of type datetime are comparable only if they have the same lt primary datetime field gt s 77 The Pyrrho Book May 2015 Intervals There are two classes of intervals One class called year month intervals has an express or implied datetime precision that includes no fields other than YEAR and MONTH though not both are required The other class called day time intervals has an express or implied inter
182. ed they should be avoided if possible Despite all of these rich possibilities it remains the case that almost all servers databases transactions and queries will be performed locally with small amounts of data Most databases will also be small enough to fit comfortably into the 4GB or so RAM available today on PCs and 1TB RAM is now available on blade servers Nevertheless Pyrrho s configuration files allow database tables and their indexes to be partitioned among a set of servers so that joins and data selected from them can be constructed on other servers We return to these ideas in chapters 9 and 10 The Pyrrho Book May 2015 Chapter 3 Database Design The physical layer of a relational database consists of a set of named base tables whose columns contain values drawn from prescribed sets of values domains Standard domains include integers fixed and floating point numbers strings of various kinds dates times etc At the layer above this the data in some of these base tables are seen as specifying entities and relations so that the rows of base tables are seen to give details of unique individual objects identified by primary keys first normal form and with relationships to other entities defined in other tables At the level above this we have the business model where these entities and their relationships serve a business purpose As mentioned in the introduction the rules of Normal Form are intended to make it easi
183. ed by the default database role and the PUBLIC standard types that have been used INTEGER and CHAR as required for these tables and the BOOLEAN standard type that the librarian used for his new Availability column Lonmecion Hear bucal son 2443 table Enkhee Pas Type Move Seeroe Cape 6 Tabka AUTHOR Lise red pa Dorus reli TEEF iti Een ra CHAR 207 Cole ma LE 321 Curera TITLE OTe shies SD sor Eclurana ANAM Ea Dumains BO LEA 65 Daisies Library The Pyrrho Book May 2015 In this table we can also see that database objects can have other role based metadata such as an output flag this can be Entity or Attribute as we will see later a human readable Description and an Iri for Web metadata In the corresponding tables for the other roles we see different metadata for different sets of objects The LIBRARIAN role renamed three of these objects and defined the Availability column and the READER role contains just a few entries As at the end of the last blog posting the database owner cannot use this role it was created by the LIBRARIAN and had not yet been made public Fred can get us the entries and also make the role PUBLIC so anyone can use it Instead of looking at the RoleSObject table for each role let s instead look at the RoleSColumn table the first is for Library the second for LIBRARIAN the third for READER Fete Up cers a E A Hmi l
184. ed in any transaction The occurrence of a transaction that modifies more than one database makes a permanent link between the databases since for example the transaction cannot be verified unless all the participating databases are online By default Pyrrho verifies such transactions for consistency each time any of the participating databases is loaded so that all participating databases must be available to the server they may of course be remote A database can be made known to the server through use of configuration files or using a connection string that refers to all of the databases The use of multifile connections is particularly interesting for the embedded editions of Pyrrho since it becomes possible to access dtabases on servers as well as on the local machine using a syntax of form file host port user role e g main myhost com 5433 admin to name the database file From the above limitations we recall that changes to remote data sources are disallowed and in addition data from different hosts must be obtained in different subqueries 10 2 Partitioning a database If a database becomes too large or too busy for the server s on which it is provided an option is to partition it to create a distributed database Ceri and Pelagatti 1984 When the partitioning is done horizontally by selecting ranges of values of fields in the primary key typically a multi column primary key is used the result is nowadays called sh
185. ed table Instead we will have procedure Claim won beat and Agree id so that the Agree procedure is effective only when executed by the loser With some simple assumptions on user names the two procedures could be as simple as Create procedure claim won int beat int insert into played winner loser values claim won claim beat Create procedure agree p int update played set agreed true where winner agree p and not agreed and loser in select m id from members m where current user like firstname 4 We want all members of the club to be able to execute these procedures We could simply grant execute on these procedures to public However it is better practice to grant these permissions instead to a role say membergames and allow any member to use this role Create role membergames Matches between members for ranking purposes Grant execute on procedure claim int int to role membergames Grant execute on procedure agree int to role membergames Grant membergames to public 5 Check the above procedures work using some sample data for example call claim 56 78 Alter the Claim procedure to record the current_date as the date of the match Alter procedure claim 6 Now create users Fred and Mary say in Windows using the Control Panel 7 Login as Fred and check that Fred select from the tables but not make changes directly Get Fred to claim a win 8 Login as Mary and accept 119
186. ee structure to disambiguate the values in a partial ordering TreeBehaviour onNullKey How the tree should behave on finding that a key is null or contains a component that is null Trees used as indexes specify Disallow for this field int depth A shortcut for spec Length SlotEnumerator lt K V gt Enumerating the entries of a tree is done using the SlotEnumerator class Like any NET IEnumerator implementation this has the following basic operations Name Description bool MoveNext move to the next entry if any return false if there is no next entry object Current this has the form Slot CurrentKey CurrentValue here but see below void Reset start the enumeration again There are currently around 100 different SlotEnumerator implementations in the DBMS including 26 special enumerators for system tables and 32 for log tables and 12 for joins of various sorts 34 The Pyrrho Book May 2015 The ATree method GetRowEnumerator returns a SlotEnumerator that traverses the pairs of the tree in key order There are two versions of this method one of which supplies a Key for matching This will enumerator all pairs where the key matches the given one Now for a strongly ordered tree no key duplicates the resulting enumeration will have 1 or zero entries a TrivalEnumerator or an EmptyEnumerator provided the key supplied will be a constant This is a very subtle and important point we wi
187. egin D 127 0 0 1 5434 11 Enter to Continue EN Command Prompt PyrrhoCmd p 5436 D Home Share View T DATA E A 2 items And the connection direct from C to A which was not in the configuration files In C s window press Enter twice 155 The Pyrrho Book May 2015 E Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S BN Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Ends with onnecting D 15 127 0 0 1 5434 Phase 4 for D 10 Enter to start i i 2 bout to Begin D 15 Enter to Continue Connecting D 9 127 0 0 1 5435 12 Protocol byte RemoteBegin About to Begin D 9 Enter to Continue 12 Protocol byte CloseConnection Closed D 9 Enter to Continue o 5 tid 3 Committed Roll r 5 Protocol byte ExecuteReader Ends with 9 About to Close D 15 Enter to Continue Connecting D 9 127 0 0 1 5435 Ficlosed D 15 Enter to Continue About to Begin D 9 Enter to Continue Connecting D 10 127 0 0 1 5435 27 0 0 1 5436 labout to Begin D 10 Enter to Continue onnecting D 17 127 0 0 5 Coordinating Commit for tid 4 About to Begin D 17 Enter to Continue RemoteTransaction D 14 Protocol byte RemoteBegin Phase 1 for D 11 Enter to start Connection 16 Coordinator 127 0 0 1 5436 Prepare sending GetMaster for D Connecting D 19 127 0 0 1 5434 gt Master About to Begin D 19 Enter to Continue Begin and Connecting D 127 0 0 1 5434 11 127 0 0
188. egin D2 13 Enter to Continue onnecting _ 127 0 0 1 5435 14 127 0 0 1 5435 EX Command Prompt OSP T p 5435 d B s 0 S 0 M 0 Command Prompt OSP T p 5435 d B s 0 S 0 M 0 start About to Begin _ 127 0 0 1 5435 14 Enter to Contin 7 Coordinating Commit for tid 6 Reconfigure _ LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 1 for _ 12 Enter to start 1 for D 13 Enter to start 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue to CheckSerialisation D2 13 Enter to Continug 1 for _ 17 Enter to start CheckSerialisation Now A starts to send the new information for the B s other connection for the configuration file EX Command Prompt OSP T p 5434 d A s 0 S 0 M 0 10 tid 8 Committed connecting D2 13 127 0 0 1 5435 About to Begin D2 13 Enter to Continue onnecting _ 127 0 0 1 5435 14 127 0 0 1 5435 EX Command Prompt OSP T p 5435 d B s 0 S 0 M 0 te IndexLo te About to Begin _ 127 0 0 1 5435 14 Enter to Contin 7 Coordinating Commit for tid 6 Reconfigure _ LocalTransaction D LocalSlave D2 ProxyTransaction _ 127 0 0 1 5435 1 for _ 12 Enter to start 1 for D 13 Enter to start 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue 1 for _ 17 Enter to start to Prepare _ 127 0 0 1 5435 14 Enter to ContjPr to CheckSerialisatio _ 127 0 1 5435 14 Ent Enter to perform CheckSerialisation for this remote
189. egrity constraints can be added or data types can be simplified for example by relaxing field size constraints Keywords that imply such sizes e g DOUBLE PRECISION BIGINT etc are not supported in Pyrrho which provides maximum precision by default National character sets are deprecated since they make data locale specific universal character sets are used by default A more important area for attention is Pyrrho s security model This offers an opportunity for improving the security of the business process Pyrrho s default settings are that the database creator s default role is the schema role and this will generally allow all desired operations to be performed But database administrators should take advantage of Pyrrho s facilities here Full details are given in Chapter 5 but the following notes provide an executive level overview of the approach The first thing to note is that Pyrrho expects the operating system to handle user authentication so that there is no way for a user to pretend to be someone else a custom encryption of the connection string is used to ensure this There is an implicit business requirement to know which staff took the responsibility for data changes corresponding to initials in former paper based systems and Pyrrho s approach is that it is undesirable for the database management system to force anonymity on such operations by disguising the staff responsible behind a faked up application identity Th
190. er to maintain the consistency of data in the database as modifications are made to it For example if the same information is contained in several rows of a table it becomes difficult to change any of these rows consistently and if we are allowed to update some of the repeated data without updating it all at once there is an obvious danger that some data will be left unchanged update anomaly Second and third normal forms ensure at least that such repeated information is no more than coincidence If a row of a table aims to provide too much information it can happen that at the point of inserting a new entry we are unable to provide information in all of the cells insertion anomaly And if some information is removed from the database but is referred to elsewhere we have a deletion anomaly Foreign key relationships can help avoid deletion anomalies However it is not really the job of the database engine to be prescriptive about such matters merely to provide the tools that the database designers want There are certain expectations about the standard data types that are supported and their interpretation in various cultures dates can be represented in different timezones international character sets and collation sequences should be used national standards for dates currencies etc It should be possible for a column to contain values of a user defined type e g with subfields or an array We will return to some of these aspects in late
191. error in aggregation operation Unexpected type for comparison with Decimal Incomparable types Loss of precision on conversion Query expected Null value found in table Null value not allowed in column Row has incorrect length Mixing named and unnamed columns is not supported The Pyrrho Book May 2015 23000 23001 23101 23102 23103 23201 23202 24000 24101 25000 25001 26000 27000 28000 28101 28102 28103 28104 28105 28106 28107 28108 2D000 2E000 2E103 2E104 2E105 2E106 2E108 2E109 2E110 2E111 2E112 2E113 2E201 2E202 2E203 2E204 2E205 2E206 2E207 2E208 2E209 2E210 2E211 2E212 2E213 2E214 2E215 2E216 2E217 2E218 2E219 2E300 2E301 2E302 2E303 201 Integrity constraint violation RESTRICT referenced in A referenced object cannot be deleted Integrity constraint on referencing table delete Integrity constraint on referencing table update This record cannot be updated usually integrity violation cannot be updated BEFORE data is not updatable Cursor status error Cursor is not open Transaction status error A transaction is in progress Invalid SQL statement name Unexpected label Triggered data change violation No role in database Unknown grantee kind Unknown grantee Adding a role to a role is not supported Users can only be added to roles Grant of select entire row is nullable Grant of insert must include all notnull columns Grant of insert c
192. ersisted data is not changed by subsequent changes to column datatypes as long as it is coercible to the new type To explain the last point suppose a table has a column of type numeric and contains values with say up to 5 signifanct digits Suppose now the table is altered so that the column is numeric 3 At this point all new values will be truncated on insertion and all existing values will be truncated on retrieval so that the table appears to contain values with a maximum of 3 significant digits Now suppose the data type is changed back to numeric Now the old data with 5 significant digits is visible once more but of course the data inserted when the data type was numeric 3 will only have 3 significant digits A case could be made that this behaviour is incorrect But it helps to avoid accidental loss of data 8 3 IRI references and subtypes Semantic information from provenance or some other source can be used to define a subtype for example a Pyrrho extension to SQL2011 allows declarations such as CREATE DOMAIN ukregno AS CHAR lt uri carregs org uk gt Subtype information can be examined using the standard SQL2011 type predicate for example SELECT FROM cars WHERE reg IS OF ukregno Pyrrho allows the notation from OWL RDF as a way of assigning an OWL type so that a value of type ukregno can be inserted in cars by writing INSERT INTO cars VALUES 1 TEA 123 4ukregno Note the use of double quotes as in
193. est will be honoured if it comes from a trusted server and the named user account matches the one in the database fragment Trusted servers are trusted to pass user identities that are the result of a windows login on the Web a STS connection strings and other connection management information is always encrypted As of v4 x Pyrrho does not encrypt normal database traffic think in vS we should allow for SSL connections for this and make use of the SecureString class internally when appropriate Now if the database is opened remotely or is partitioned the assumption is that the user identities in the database make sense somehow to any access of the database i e the connection string potentially mentions users who are mentioned in the database So for example any user connecting to the database should be entitled to some access to all fragments At least the server they connect to should be able to validate their access thus any Query role server must be able to authorise users If a Pyrrho server succeeds in loading a database for the Query role this means that it has succeeded in gaining access to all the fragments needed and that there is an agreed list of trusted servers Any request is trusted only if the effective user identity is in the relevant database and has the relevant permissions This analysis already leads to some new ideas that establishing the Query role for a database will be checked when the database is loaded or reloa
194. ew lt DATA E gt A A Now in the PyrrhoCmd window insert into E values 4 7 EN Command Prompt osp T p 5434 d A s 0 S 0 M 0 PyrrhoDBMS protocol on 127 0 0 1 5434 Database folder MAY Connection 1 Files D User asusrog Student 1 Protocol byte ExecuteReader DbStorage Flush complete for A D osp len 55 1 Coordinating Commit for tid 1 LocalTransaction D Phase 1 for D 4 Enter to start Phase 1 5 for D 4 Enter to start Phase 2 for D 4 Enter to start Phase 3 for D 4 Enter to start StartCommit for D osp at 50 DbStorage Flush complete for A D osp len 137 Phase 4 for D 4 Enter to start 1 tid 1 Committed 1 Protocol byte ExecuteReader 1 Coordinating Commit for tid 2 LocalTransaction D Phase 1 for D 5 Enter to start EM Command Prompt PyrrhoCmd p 5434 D KO Home a Pe MBE MOSP gt PyrrhoCmd p 5434 D QL gt create table E F int primary key SQL gt insert into E values 4 7 In the A server window press Enter five times 130 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 M 0 OSP T d C p 5436 s 0 S 0 M 0 E x EM Command Prompt PyrrhoCmd p 5434 D Fie Home Share View veo OSP gt Py d p 5434 I e t E DATA E gt A POES insert tote E vales Name LJ D osp In the PyrrhoCmd window we close the session with C and the server acknowledges the end of the Connection 1
195. exConstraint level 2 It is done at level 2 for speed during transaction commit and consists of a linked list of the following data which is stored in a non persisted field of the new Record e The set of key columns e The table defpos e The new key as a linked list of values e A pointer to the next IndexConstraint During LocalTransaction AddRecord and LocalTransaction UpdateRecord a new entry is made in this list for the record for each uniqueness or primary key constraint in the record When the Record is checked against other records and discussed next this list is tested for conflict Referential Integrity The main referential integrity mechanism is contained in LocalTransaction However a final check needs to be made at transaction commit in case a concurrent transaction has done something that violates referential integrity If so the error condition that is raised is transaction conflict rather than the usual referential integrity message since there is no way that the transaction could have detected and avoided the problem Concurrency control for referential constraints for Delete records are handled by ReferenceDeletionConstraint level 2 It is done at level 2 for speed during transaction commit and consists of a linked list of the following data which is stored in a non persisted field of the Delete record e The set of key columns in the referencing table e The defining position of the referencing table
196. eys to check that a duplicate key has not been added since the start of T b to check that a key referenced by an inserted record has not been deleted since the start of T and c to check that a key we are deleting is not referenced by a record that has been inserted since the start of T Needless to say as soon as we start to check the effects of other transactions isolation is over so such checks can only be made during T s commit and all the steps described in the last two paragraphs must be done before any other transaction can start to commit Pyrrho goes to a lot of trouble to reduce the amount of processing needed to carry out these checks but inevitably the cost of performing the checks is linearly dependent on the number C of changes by T and also on the number D of physical changes by other transactions since the start of T The cost R of read constraints in T is a bit better than linear in the number of records read R increases by 1 for each table all of whose records are read and for each specific record read The total cost of guaranteeing serialisability is O CD D ogR In some ways given the commitment to transaction safety Pyrrho s design is near optimal and even works well for distributed databases and transactions It is not excessive as the benchmarks in Lecture 1 show but people are not used to paying for this level of serialisability There are alternative approaches If the transaction contains only updates SSI d
197. f possible displays the code appropriately for the viewing role There are four blank columns in these tables Update can specify a set of actual assignments to be carried out if a generated column is assigned to The next three columns are used for reverse relationship navigation and are specified using Pyrrho s new REFLECTS syntax Let s examine the list of users allowed to login to roles this SysSRoleUser table looks the same from any role allowed to see it Cansscion Hear lechal san 1i otitis Libre nbb asi er table Ecih Role her LERAREN TOPE Library MAL READER quen REAR TOM 67 The Pyrrho Book May 2015 guest appears in this list because Fred has ordered grant reader to public Finally in this section I d like to show some entries from what the database file actually contains These are from the Logs table The first shows where create the LIBRARIAN role and grant all privileges on table AUTHOR with grant We can see that both these transactions are by Role 4 which is the default role for the database always the first database object to be created User 35 is TORE Malcolm the database creator So role Library is defining the librarian role Granting all privileges on the AUTHOR table unless it is restricted to a particular set of columns implies granting all privileges on all the columns too And all privileges means all the privileges held by the grantor in this case also al
198. following commands in a Gnome Terminal window Pyrrho Server cd opt OSP mono OSP exe For client sessions in following experiments open 2 parallel Gnome Terminal windows starting the client using following commands Pyrrho Client cd opt OSP mono PyrrhoCmd exe TestDB SS SS SS SS SS On Windows REM Pyrrho Server on Windows Unzip Pyrrho zip to C Temp Pyrrho CD Temp Pyrrho Pyrrhosvr REM Pyrrho Client on Windows CD Temp Pyrrho 107 The Pyrrho Book May 2015 Start osp in one window and start pyrrhocmd in another PyrrhoCmd testdb Here s an example of the sort of thing that went wrong Note that in the comments above on Linux the instructions say to call the database TestDB Whoever wrote the instructions clearly reasoned that Windows file names are not case sensitive This is not actually true If the database is really called TestDB then the above command will result in lots of error messages To check this try creating a database in one case and then get the case wrong as in C OSP gt pyrrhocmd MixedCase SQL gt create table ath int gt SQL gt C C OSP gt pyrrhocmd mixedcase SQL gt table a Could not use database mixedcase osp database not found or damaged gt GOL m Actually this used to cause all sorts of internal errors Notes As DEFAULT Pyrrho uses AUTOCOMMIT mode Pyrrho does not accept the word WORK after COMMIT SMALLINT is not a supported data t
199. for 274 lt 2841 1 gt lt 3241 1 gt lt 368 Dombey amp Son gt 1444 Record for 274 lt 2841 2 gt lt 3241 1 gt lt 368 Nicholas Nickleby gt 1488 Record for 274 lt 2841 3 gt lt 3241 2 gt 368 Nostromo 1523 PTransaction for 1 Auth 4 User 32 Time 23 05 2007 19 36 12 1539 Record for 274 lt 2841 4 gt lt 3241 2 gt 368 Heart of Darkness 1583 PTransaction for 1 Auth 4 User 32 Time 23 05 2007 19 36 53 1599 Update of 485 4M5 gt Record for 274 lt 3681 Dombey and Son 1634 PTransaction for 1 Auth 4 User 32 Time 23 05 2007 19 31 12 658 Delete Record Record for 274 lt 2841 3 gt 3241 2 gt lt 3681 Nostromo gt gt 488 The system log refers to columns and tables by their uniquely identifying number rather than by name Note also that the Update record shows which field s have been modified Most of the System and log tables have a column called Pos which gives the defining position of the relevant entry There is a pseudo column in every table called POSITION which allows the defining position of current records in the database to be retrieved using ordinary queries e g in the above example select book position from book where title Dombey and Son would give 405 This value is in fact the defining position of the first record with the same primary key as Dombey and Son rather than the place where the current title was set and so it can be used to find other relevant log entries
200. for example POST does not even return data All tables referenced by selectors must have primary keys For example with an obvious data model GET http Sales Sales Orders 1234 returns a single row from the Orders table GET http Sales Sales Orders Total gt 50 0 OrderDate distinct returns a list of dates when large orders were placed GET http Sales Sales Orders OrderDate Total returns just the dates and totals GET http Sales Sales Orders 1234 of Orderltem returns a list of rows from the Orderltem table and GET http Sales Sales Orders 1234 CUST Customer NAME returns the name of the customer who placed order 1234 The response will contain a list of rows if HTML has been requested it will display as a table or a chart if specified by the Metadata flags sec 7 2 Using HTML will also localise the output for dates etc for the client Metadata can also specify XSL transforms so that simple business objects can be generated directly by Pyrrho PUT http Sales Sales Orders 1234 DeliveryDate with text plain content of date 2011 07 20 will update the DeliveryDate cell in a row of the Orders table PUT content consists of an array of rows 8 The optional keywords here are less restrictive than might appear In this syntax views and tables can be used interchangeably so that the keyword table if present may be followed by a view Similarly the keyword procedure if present may be followed by a function call 70 The Pyrrho Book May 2
201. for this record ES EN Command Prompt PyrrhoCmd kee An authorisation identifier is like a user Users are defined in SQL by granting them privileges It is assumed that there is some implementation defined way of associating a particular session with an authorisation identifier For example in SQL server users are defined within SQL server or by means of Windows integrated authentication In Pyrrho the user identity is taken from Windows in form domain user or in Linux from the connection string and cannot be changed in a session SQL recognises a predefined authorization identifier SYSTEM Apart from _SYSTEM any authorisation identifier can be a granted privileges or roles 56 The Pyrrho Book May 2015 6 3 Privileges The SQL standard says that a privilege authorises a given category of action to be performed by a specified authorisation identifier on a specified object such as a table a column a domain a user defined type or a routine The actions that can be specified are insert update delete select references usage under trigger and execute Insert update select and references can be for whole tables or views or can be limited to a specified set of columns Usage privileges apply to domains or user defined types Under privileges apply to structured types and execute privileges apply to routines The security model in the SQL standard is based on the GRANT and REVOKE statement There are two
202. g Relationships In the Foreign Key Relationships dialogue click Add Click on Tables and Columns Specific and click the ellipsis button Change the Primary Key table to Member and select Id and select winner as the Foreign Key Table column Click OK and click Add again for Loser Click Close and Save the tables To place data in the tables right click the tables and select Show Table Data When you enter the date in the playedon field the date format is dd mm yyyy the other way round from MySQL Add a DataSet to the project and drag the Members table onto it This time when you add the DataGridView click Choose Data Source and browse down to get DataSet1 gt Member Adjust the size so you can see all three columns If you now view code you will see that a member table adapter already has been configured to load the data into the DataGridView 7 As before we need to implement a way of updating the database This time the code we want in RowValidated is memberTableAdapter Update dataSet1 Member 101 The Pyrrho Book May 2015 8 Once again add the two gadgets we had in the last tutorial a textbox and a combobox The code of the textbox is identical to the previous time 9 For the comboBox we can set up the Items as follows comboBox1 Items Clear var rdr database1DataSet CreateDataReader while rdr Read comboBox1 Items Add rdr 1 ToString Note that the connection string to the dataset is D
203. g exercised so that the action can be checked for validity The principles of transparency and accountability mean that people need to explain what they are doing it is not enough simply to say am doing this because can Security analysis begins with an account of who is allowed to enter or modify data and on what basis and who is allowed to read that data Permissions can be granted to applications as well as to users but in that case the application takes on the responsibility for allowing different individuals to carry out different operations and for best results it is these that should be recorded in the transaction record For a particular database and application it will be clear at any stage what role is being exercised The same considerations apply to stored procedures and to methods of structured types From this discussion we see that database operations should be granted to roles and roles should be granted to users In SQL there is also the possibility of allowing users to administer a role and allowing a role to grant privileges to other roles For an example suppose we have a warehouse containing products being ordered by customers We can imagine that the list of products is maintained by a Manager role that a Clerk can add a new customer or take a new order that a Storeman can manually alter stock levels that a Deliveryman can record that a delivery has been done etc We expect none of this information is confidentia
204. gh to send a message In these cases the messages between client and server are simple and text based For email there are headers such as To From and Subject followed by the message body For web servers the first line of the request contains a verb and a URL and the last line is blank while the response begins with a status code then headers a blank line and then the body of the response PUT and POST requests also have a body following the blank line Services almost always listen on well known port numbers although there is always the option that servers and clients agree on the use of some other port These port numbers are assigned by the Internet Assigned Numbers Authority www iana org so you can look up the one you want Even Pyrrho has its own port number of 5433 On a PC you can see what listeners are in operation by using netstat a b If you see an IP address in square brackets with s in it this is an IPv6 address e g 39 The Pyrrho Book May 2015 4 3 The application protocol Once the application s 2 way channel is established ordinary I O operations for Steams can be used The size of the first packet received is used in the end to end TCP packet negotiation For many TCP IP services e g HTTP there is only one message in each direction so this is fine But if there will be many messages it is important to remember that the packet size negotiation is done again if the packet size changes For
205. gin col byte Fetch Connection 14 Coordinator 127 0 0 1 5435 Files _ Password password Role A n D 15 Enter to Continue 14 Protocol byte RemoteBegin Pr 14 Protocol byte IndexLookup 14 Protocol byte IndexNext 14 Protocol byte IndexNext Connection 16 Coordinator 127 0 0 1 5435 Files D Role User guest Connecting _ 127 0 0 1 5435 14 127 0 0 1 5435 About to Begin _ 127 0 0 1 5435 14 Enter to Continue gt o 2 er to start onnecting D2 13 127 0 0 1 5435 14 Protocol byte IndexLookup 14 Protocol byte IndexNext 14 Protocol byte IndexNext About to Begin D2 13 Enter to Continue 16 Protocol byte RemoteBegin 16 Protocol byte CloseConnection xception 00000 ER Rollback 16 Ends with 9 14 Protocol byte IndexLookup 14 Protocol byte IndexNext 14 Protocol byte IndexNext onnection 18 Coordinator 127 0 0 1 5435 Files D Role User guest 18 Protocol byte RemoteBegin onnection 20 Coordinator 127 0 0 1 5435 Files D Role User guest 20 Protocol byte 20 Protocol byte 20 Protocol byte 20 Protocol byte 20 Protocol byte RemoteBegin IndexLookup IndexLookup IndexNext IndexNext E DATA E gt A D osp Bl I8 Home Share View t E DATA E gt B Enter to start e D 15 Enter to Continue Enter to Continue 14 Ente start D 18 Enter Enter t or D Enter to Committ 1 by D 15 127 6 gin D 15 E o Continue g D 21 127 0 o Continue
206. gs about uploads and downloads e command Use the given command instead of taking console input Then the SQL gt prompt is not used f file Take SQL statements from the given file instead of from the console b No downloads of Blobs Show this information and exit Pyrrho can support locales other than English but such localisations are not currently included in the distribution Whether the command prompt console window is able to display the localised output will depend on system installation details that are outside Pyrrho s control Localisation is more effective with Windows Forms or Web Forms applications The SQL gt prompt PyrrhoCmd is normally used interactively At the SQL gt prompt you can give a single SQL statement There is no need to add a semicolon at the end There is no maximum line length either so if the command wraps around in PyrrhoCmd s window this is okay 11 The Pyrrho Book May 2015 SQL gt set role ranking Unless you use multiline command as described below be careful not to use the return key in the middle of an SQL statement as the end of line is interpreted by PyrrhoCmd as EOF for the SQL statement At the SQL command prompt instead of giving an SQL statement you can specify a command file using filename Command files are ordinary text files containing an SQL statement on each line If wraparound annoys you then you can enclose multi line SQL statements in and must the
207. h The Pyrrho Book May 2015 2E304 2E305 2F003 2H000 34000 34001 3D000 3D001 3D002 3D003 3D004 3D005 3D006 3D007 3D008 3D009 3D010 40000 40001 42000 42101 42102 42103 42104 42105 42106 42107 42108 42109 42110 42111 42112 42113 42114 42115 42116 42117 42118 42119 4211A 42120 42121 42123 42124 42125 42126 42127 42128 42129 42130 42131 42132 42133 42134 42135 42136 42137 202 Get rurl should begine with No data returned by rurl Prohibited SQL statement attempted Non existent collation Collate on non string No such cursor Cursor is not updatable Could not use database database not found or damaged Database not open Cannot detach preloaded databases Remote database no longer accessible Exception reported by remote database Requested operation not supported by this edition of Pyrrho Database incorrectly terminated or damaged Pathname not supported by this edition of Pyrrho Database file has been damaged Automatic database recovery from file damage failed Invalid Password Transaction rollback Transaction Serialisation Failure Syntax error at Illegal character Name cannot be null Key must have at least one column Proposed name conflicts with existing database object e g table already exists Access denied Undefined variable Table undefined Procedure not found Table valued function expected Column list has incorrect length expected g
208. h 9 Protocol byte IndexNext Connection 4 Coordinator 127 0 0 1 5435 Fileg Protocol byte CloseConnection 4 Protocol byte RemoteBegin Exception 00000 4 Protocol byte CloseConnection 2 Rollback Exception 00000 About to Close D 5 Enter to Continue 4 Rollback Closed D 5 Enter to Continue 4 Ends with 9 2 Ends with 9 1 Coordinating Commit for tid 1 Reconfigur RemoteTransaction D ProxyTransaction _ 127 0 0 1 5435 Phase 1 for _ 5 Enter to start Phase 1 for D 7 Enter to start About to Close D 5 Enter to inue Closed D 5 Enter to Continue EX Command Prompt PyrrhoCmd Fie Home Share View Ata as p 5436 _ SQL gt insert into _Database values D 127 0 password 127 0 0 1 5435 DATA E A password p 5436 _ Name Da Now press Enter on C three times 146 student The Pyrrho Book May 2015 s l BW Command Prompt OSP T d C p 5436 s 0 S 0 M 0 OSP gt osp T p 5434 d A s S M 0 byte Fetch StartCommit for _ osp at 34 T p 5434 d A s S 0 Coordinator 127 0 0 1 5434pnstorage Flush complete for C _ osp len Pyrrho DBMS c 2015 Protocol byte RemoteBegin Phase 4 for _ 4 Enter to start Protocol byte IndexLookup 3 tid Committed PyrrhoDBMS protocol on 127 0 0 Protocol byte IndexNext Connecting D 5 127 0 0 1 5435 atabase folder MA Protocol byte IndexLookup About to Begin D 5 Enter to Continue Protocol byte IndexNext Connecting 0
209. hen its changes are written to durable media not the time of the commit request for example as in Pyrrho by flush writes to the transaction log To ensure this serialisability is valid we need to ensure that all of the records we have accessed some of which we may be about to change still have the values found in the snapshot taken at the start of the transaction Thus a first requirement at commit time of a transaction T is to ensure that none of this data has been modified by other commits since the start of T The set of read records and proposed physical changes is checked against physical changes that other transactions have committed since the start of T The first part the read records is handled by a list of read constraints maintained by the local transaction For changes the proposed physical records about to be written to disk are checked against those that have been committed to the database since the start of T For example if we are updating a value we need to be sure that the table and record are still there and the column still exists and has the right type These checks guarantee consistency of the database There are three further checks that are needed to guarantee data integrity The DBMS will already have checked for entity and referential integrity against the values it has in the snapshot but at commit time checks are needed against any relevant changes committed by other transactions These are a for primary and unique k
210. here the tables being joined are related using an adapter function see section 5 2 1 and then both sets of named columns are in the result rowset JoinType INNER LEFT RIGHT FULL OUTER SearchCondition BooleanExpr OrderByClause ORDER BY OrderSpec OrderSpec OrderSpec Value ASC DESC NULLS FIRST LAST The default order is ascending nulls first FetchFirstClause FETCH FIRST int ROW ROWS ONLY XmIColumns COLUMNS XmlColumn XmiColumn XmlColumn id Type DEFAULT Value PATH str A6 6 Value Value Literal Value BinaryOp Value Value Value Value Collate Value Value Value AS Type ColumnRef VariableRef SYSTEM_TIME Period_id PERIOD Value Value VALUE ROW Value Member_id MethodCall NEW MethodCall FunctionCall VALUES Value Value Y 4 Value Value 191 The Pyrrho Book May 2015 QueryExpression Subquery ROW Value Value Y mongo_spec F MULTISET ARRAY Value Value Subquery TREAT Value AS Sub_ Type Y CURRENT_USER CURRENT_ROLE HTTP GET url_Value AS mime_string The VALUE keyword is used in Check Constraints ROW if not followed by can be used for testing the type of the currently selected row Subqueries that are mulitset valued must be part
211. hese do not correspond to proposed changes to the database Data recorded in the database is intended to be non localised e g it uses Unicode with explicit character set and collation sequence information universal time and date formats and machine independent e g no built in limitations as to machine data precision such as 32 bit Default value expressions check constraints views stored procedures etc are stored in the database in SQL2011 source form and reparsed when required This has the advantage that changes consequential on renaming of objects can be supported at the logical database level where the edits can be applied to the source forms in memory The database implementation uses B Trees throughout note B Trees are not binary trees Lazy traversal of B Tree structures enumeration is used throughout the query processing part of the database This brings dramatic advantages where search conditions can be propagated down to the level of B Tree traversal Database values are strongly typed TypedValues but during query processing the server works with SqlValues which are expressions obtained from the query language An SqlValue can be evaluated in a Context to get a TypedValue Thus a Query is a context whose RowSet is a row of SqlValues an SqlRow with a RowEnumerator which modifies the values of the row columns as it moves This matches well with the top down approach to parsing and query processing that is used throughou
212. idated object sender DataGridViewCellEventArgs e cellChanged e ColumnIndex true if newRow var r dataGridView1 Rows e RowIndex int TryParse r Cells 0 Value ToString out id A1 6 Using Java with Pyrrho There are several analogues to Windows Forms in Java such as Swing But just for fun let s do a very simple console application that retrieves data from a database You will need the Java Development Kit JDK installed on your computer The Pyrrho distribution includes a library called OSPJC First set up the Path and CLASSPATH environment variables Start with Computer gt Properties gt Advanced System Settings gt Environment Variables and use Edit and New respectively Add the following to Path C Program Files x86 Java jdk1 7 0_09 bin Set CLASSPATH to 3C Program Files x86 Java jdk1 7 0 09 lib C PyrrhoDB OSP OSPIJC bin Alternatively copy the org folder in OSPC bin to the current directory and use cp with the javac and java commands below The following program assumes that database Temp has a table called A with columns B int and C char Use Notepad or something to make a test program JCTest java and remember to use All files when saving import org pyrrhodb Connection import java sql Statement import java sql ResultSet public class JCTest public static void main String args throws Exception Connection conn Connection getConnection localhost Temp COMP10059
213. ield SECOND int DateTimeField StartField SECOND int int y The ints here represent precision for the leading field and or the fractional seconds IntervalField YEAR MONTH DAY HOUR MINUTE A6 7 Boolean Expressions BooleanExpr BooleanTerm BooleanExpr OR BooleanTerm BooleanTerm BooleanFactor BooleanTerm AND BooleanFactor BooleanFactor NOT BooleanTest BooleanTest Predicate BooleanExpr Y Boolean_Value Predicate Any Between Comparison Contains Every Exists In Like Like Regex Member Null Of PeriodBinary Similar Some Unique Any ANY DISTINCT ALL Value FuncOpt Between Value NOT BETWEEN SYMMETRIC ASYMMETRIC Value AND Value Comparison Value CompOp Value CompOp lt gt lt gt lt gt Contains PeriodPredicand CONTAINS PeriodPredicand DateTime_Value Every EVERY DISTINCT ALL Value FuncOpt Exists EXISTS Table _Subquery XMLEXISTS XmlQuery Y 193 The Pyrrho Book May 2015 FuncOpt FILTER WHERE SearchCondition OVER WindowSpec The presence of the OVER keyword makes a window function In accordance with SQL2011 02 section 4 15 3 window functions can only be used in the select list of a QuerySpecification or SelectSingle or the order by clause of a simple table query
214. ies Laii epee alee erae ti tea ars de bapak tr e o Tete als ise boot edd Aral boca delei ir sei ite Asia Arade bom boci P cholso Hiriy Dibra Te create role reader grant select Title Author Availability on book to reader Cone hon Hpt icat a II Dabe biy bean a gari seif Tote Pta add en book da reada The only columns the Reader can see are the ones granted so Reader can say simply table book to see these 63 The Pyrrho Book May 2015 cl Perro S i Connector Hai loved Port MI Daata Library ir bose Aru Sauilbdry Load bv Bichel Horta Ditema Terr Note that the Author data comes from a table that is otherwise inaccessible to the Reader because the generation rule uses definer s rights Now this is how things stand The database objects as viewed from the default Library role have not changed Conor Heer locals lan HII Cobb Limay v H Fe tabh tet 1D TITLE 16 Lord hm p T 11 Meha Pech ber 1 From the Librarian role we have 64 The Pyrrho Book May 2015 UNES Domein Hear echa sn Si Gabbe eee Calais Library v coran Rode BEA and as we have seen the Reader does not see the numeric fields 7 1 How the mechanism works The database creator has set up the following objects in the Library database AUTHOR ID NAME and BOOK ID TITLE AID ANAME In the RoleSObject system table we can see these objects as own
215. if NULLIF Value Value Occurrences_Regex OCCURRENCES REGEX Pattern_Value FLAG Options Value IN String Value FROM StartPos_ Value USING CHARACTERS OCTETS Percentile PERCENTILE_CONT PERCENTILE_DISC Value WithinGroup WindowSpec Window_id WindowDetails WithinGroup WITHIN GROUP OrderByClause y Position POSITION Value IN Value Without parameters POSITION gives a Pyrrho log entry see section 3 5 Position_Regex POSITION_REGEX START AFTER Pattern_Value FLAG Options_Value IN String_Value FROM StartPos_Value USING CHARACTERS OCTETS OCCURRENCE RegexOccurrence_Value GROUP RegexCaptureGroup_Value PowerFunction POWER Value Value Y Rank CUME_DIST DENSE_RANK PERCENT_RANK RANK OVER WindowSpec DENSE_RANK PERCENT_RANK RANK CUME_DIST Value Value WithinGroup Regression REGR_SLOPE REGR_INTERCEPT REGR_COUNT REGR_R2 REGR_AVVGX REGR_AVGY REGR_SXX REGR_SXY REGR_SYY Value Value FuncOpt RowNumber ROW_NUMBER OVER WindowSpec Schema SCHEMA ObjectName COLUMN id 195 The Pyrrho Book May 2015 Added for Pyrrho returns a number identifying the most recent schema change affecting the specified object including any change to this object by another name in another role
216. ify this has worked in the usual way select from members etc 102 The Pyrrho Book May 2015 OSP Shortcut 4 8 28 March 2813 www pyrrhodb com OT Min k Reads ted on port 8186 rted on port 8133 S protocol using port 5433 on iC Temp OSP48 0S8P gt pyrrhocmd club SQL gt create table memberCid int primary key fi ame char surname char gt ID expected at member SQL gt create table Members id int primary key firstname char surname char SQL gt insert into members 56 Fred Bloggs gt IRPAREN expected at SQL gt insert into members values 56 Fred Bloggs gt i st into members values 78 Mary Black gt ate table played id int ary key playdon date winner int references m oser int references members agreed boolean i played values 32 date 2814 81 89 56 78 false gt Now start up Visual studio and make a new Windows Forms project Change the target framework to NET 3 5 This time add Reference and browse to C Temp OSP48 OSP OSPLink dll Remove the reference Microsoft CSharp In the two cs files in the project delete the using lines for System Threading Tasks and add using Pyrrho As before place a DataGridView in the design surface Double click the design surface outside of the DataGridView In the class declare PyrrhoConnect conn In the Form1 constructor method add the lines conn new PyrrhoConnect Files club conn Open In the Form1_Lo
217. ii View O0SP gt PyrrhoCmd p 5436 _ SQL gt insert into _Database values D 127 0 0 1 5436 2 password 127 0 0 1 5435 student 3 lt DATA E A password Since D will be a new database for C C needs to read all of the data coming from B and construct all of the indexes required to provide a query service We can see it has fetched data from B Press Enter on C 145 The Pyrrho Book May 2015 Command Prompt osp T p 5434 d M E Command Prompt OSP T d B p 5435 l EX Command Prompt OSP T d C p 5436 OSP gt osp T p 5434 d A M 0 5 2 19 March 2015 www pyrrhodb com T p 5434 d A s 0 M Enter to starConnecting D 3 127 0 434 ecoutinure Pyrrho DBMS c 2015 Malcolm Crowe and UniverAbout to Begin D 3 Enter to Continue phase 1 for 4 Enter to start 5 2 19 March 2015 y pyrrhodb com Closed D 3 Enter to Continue Phase 1 5 for _ 4 Enter to start PyrrhoDBMS protocol on 127 0 0 1 5434 PyrrhoDBMS protocol on 127 0 0 1 5435 phase 2 for _ 4 Enter to start jatabase folder MAN Database folder y Phase 3 for _ 4 Enter to start Connection 2 Coordinator 127 0 0 1 5435 FilesConnection 2 Coordinator 127 0 0 1 5434startCommit for _ osp at 34 2 Protocol byte RemoteBegin Connecting D 5 127 0 0 1 5434 DbStorage Flush complete for osp len 979 2 Protocol byte CloseConnection About to Begin D 5 Enter to Continue phase 4 for _ 4 Enter to start _ Exception 00000 2 Protocol byte RemoteBegin 3 tid
218. ill build in role based support for the standard business procedures it supports but very few do Most DBMS s simply allow anyone with the power to do something to do it and don t provide a mechanism to track the roles being played In Pyrrho the transaction record includes not only the user identity for a transaction but the role A user can only use one role at a time for any given database Roles should capture and restrict to normal business operations If it becomes necessary for intervention to correct some unusual condition some administrative role with greater permissions can be used Auditing will highlight these and they might usefully indicate a need for process improvement Moorthy et al 2011 2 3 Consistency Consistency means that the data does not contain any contradictions In good database design a first step in this direction is to minimise copied data if information is repeated in different places it become hard to ensure consistency when that information changes Dependent information e g total or count should be correct when it is accessed In line with the no copies rule it is actually best if a sum or count is recomputed when required rather than if an old value is stored somewhere As mentioned above in many DBMS a single transaction results in many changes to data files many of which are effectively copies e g a new row in a table would typically have the new primary key value stored in several places
219. imary keys for table FOR EACH ROW not specified Cannot specify OLD NEW TABLE for before trigger Malformed SQL input non terminated string Bad join condition Column must be aggregated or grouped Table already exists Unimplemented or illegal function Nested types are not supported Column is already in table END label does not match start label is not the primary key for is not a foreign key for has no unique constraint expected at Table period definition for has not been defined Generated column cannot be used in a contraint Table has no primary key Versioning for for table has not been enabled Domain already exists A routine with name and arity already exists Check condition fails Domain check fails for column in table Table check fails for table Column check fails for column in table Column in Table contains null values not null cannot be set Column in Table contains values generation rule cannot be set The Pyrrho Book May 2015 Appendix 8 Pyrrho s System Tables There are three sets of system tables and these give read only access using SQL for the database owner to internal information held in the DBMS engine as seen from the current transaction For more details see the Pyrrho Manual Pyrrho docx Since the names of these tables contain a they need to be enclosed in double quotes in SQL For some of the tables the information is for th
220. in value expressions to refer to other fields e g a Sx would set field a to the value of field x We also see here that we can get select expressions to construct new documents for us In simple cases the resulting documents look like the one in the select statement but with all these special operators in this case the resulting document looks like the following _id v 1 ok true result age 19 count 4 age 20 count 3 age 24 count 1 Updates are actually quite complex in MongoDB and the use of special operators is inescapable For example the Sset operator is used to add fields to a document In Pyrrho we can allow update people set doc Sset friend Fred where doc name sue Use these forms to explore the mappings given in the Mongo DB documentation 3 8 Pyrrho DBMS low level design In this section we discuss some of the fundamental data structures used in the DBMS The data structures in this section have been chosen because they are sufficiently complex or unusual to require such discussion Obviously this section can be skipped at a first or even later reading 32 The Pyrrho Book May 2015 B Trees Almost all indexing and cataloguing tasks in the database are done by BTrees These are basically sorted lists of pairs key value where key is comparable In addition sets and partial orderings use a degenerate sort of catalogue in which the values are not used and are all the single
221. ing to the current role create table author id int primary key aname char create table book id int primary key authid int title char create function booksby auth char returns table title char return table select title from author a inner join book b on a id b authid where aname booksby auth This example also shows that a routine body is a single procedure statement possibly a compound BEGIN END statement If you use the command line utility PyrrhoCmd very long SQL statements 80 The Pyrrho Book May 2015 such as the last one above can be enclosed in square brackets and supplied on several lines as described in section 1 7 The above function can be referenced by statements such as select from table booksby Charles Dickens The keyword table in this example is required by SQL2011 2 7 6 However methods of a structured type van have a returns clause 8 9 Condition handling statements The following condition handling apparatus as specified in SQL2011 is also supported The predefined conditions are SQLSTATE string SQLEXCEPTION SQLWARNING and NOT FOUND but any identifier can be used All of the following can appear where statements are expected and handlers apply anywhere in the scope where they are declared DECLARE CONTINUE HANDLER FOR conditions statement DECLARE EXIT HANDLER FOR conditions statement DECLARE UNDO HANDLER FOR conditions statement UNDO is defined in the SQL standard 04 4 8
222. interoperability so that the data formats will still make sense years from now In laboratories we have been looking at how databases can be accessed from a variety of languages and systems In the labs we have been using Windows systems but as many of you will know the computing industry has been very careful to ensure that systems can work together over the Internet TCP IP is a good start and helps overcome many difficulties by enabling clients and servers to communicate Java and PHP are available on all platforms and even C is available on Linux if the Mono runtimes are installed In particular we have looked at how the very different worlds of NET and PHP can communicate There are many examples today of non relational and NoSQL database systems All of these for various reasons depart from the standard SQL and relational database design Some of these issues were discussed earlier in this course The point of view strongly expressed in this book is that relational DBMS offer a valuable general purpose data management infrastructure and that their most valuable benefits are the ACID properties especially consistency and durability One of the more interesting NoSQL databases today is MongoDB MongoDB provides schema less data management for JSON like documents identified by a special _id key and there are some notes in the following based on the documentation available on https www mongodb com To select a document
223. ion that wishes to use the Open Source Pyrrho DBMS and PyrrhoLink dll is needed by any application that wishes to use the Professional edition of the Pyrrho DBMS These client libraries have similar functionality This library includes support for client applications The simplest possible approach is simply to place PyrrhoLink dll or OSPLink dll in the same folder as the application that is using it PyrrhoCmd is a console application for simple interaction with the Pyrrho server Basically it allows SQL statements to be issued at the command prompt and displays the results of SELECT statements in a simple form For most purposes it is best to place the command line utilities such as PyrrhoCmd and the client dll in a different location from the server They occupy very little disk space and the databases will be created in the server s folder With embedded databases things are different Databases will be in the same folder as applications using an embedded edition of Pyrrho 1 6 Checking it works For simplicity on the same machine as the server open a command window and use cd to navigate to the same folder as the client executable Be sure to use the correct version of PyrrhoCmd you cannot use the professional version of PyrrhoCmd with the open source server or vice versa It is not usually a good idea to start up PyrrhoCmd or the server by double clicking because the command line parameters can be useful PyrrhoCmd SQL gt table
224. is but we don t use the SERIES keyword any more Things like HISTOGRAM PIE X Y are keywords For example assuming table mytable has suitable data columns mycaptions and mycolumn alter table mytable histogram alter table mytable alter column mycaptions x alter table mytable alter column mycolumn y 120 The Pyrrho Book May 2015 Use the HTTP REST service to view the histogram in a browser the URL you want is of form http localhost 8180 mydb myrole mytable If your database has no roles defined yet the default role has the same name as the database 5 The rules for case sensitivity come separately from Windows and SQL and are a little confusing In the command line and the URL the database file name and thus the name of Pyrrho s default Role are case sensitive By default lower case letters remain in lower case So if you create a database called mydb the actual file name on the server will be mydb osp If you need to use these lower case identifiers in SQL you need to enclose them in double quotes The default role for example will be mydb In SQL the names of database objects that you create are not case sensitive unless they are enclosed in double quotes In the absence of double quotes lower case letters will be turned into upper case If you create a table called mytable in SQL the actual name will be MYTABLE and so if it is mentioned in a URL you will need to use ca
225. is means that users of the database must be identified and granted permissions Where the number of authorised staff is large mechanisms for authorising new users can be automated Generally it is useful to use the role mechanism to simplify the granting of groups of permissions to the users Generally a role should be created with the same rights as each application in the legacy system Existing users and roles can be imported from the existing database assuming users are identified in the existing database by their login identities Where applications have been given user identities in the legacy system this should generally be replaced by roles Ideally each business process should have a role to enable associated database changes to be tracked Each connection to Pyrrho is for a role and this can enable a good record of the reasons for changes to data 7 3 The REST service By default Pyrrho will try to set up a REST service on ports http 8180 and https 8133 using Windows authentication You can supply your own server certificate for transport layer security and or specify different ports Users who have not been granted roles in the database will be able to access public data From the viewpoint of this book the importance of considering these features here is that the results are delivered by the standard database engine so that any updates will be subject to the same access control constraint checking triggers etc proto host port
226. is not present it assumes it is an isolated server that is it has Master Storage and Query roles for any database that is opened If the database is present then it can specify the roles that this server has for each of a number of databases If the role is not the default Master Storage Query then the local configuration database should also specify another server that will be trusted to help with that database and optionally a set of credentials to use for that database If a database is partitioned then the base server may be specified If we are the base server then a set of partitions we know about should be specified For partitions on other servers we need connection information in the form host port but not credentials as the current user credentials should work A server may have different roles for different partitions of the database It will trust any host or domain mentioned in the configuration database More than one server may be opened on a single machine or by a single user on different machines If the server loads a database and the checksum checks out then users mentioned in form domain user or host user in the database will have their assigned permissions on this database The user who requests a connection to the database if mentioned in the database will have the assigned permissions otherwise will have the permissions assigned to PUBLIC This will also apply when the database is opened by a remote server The requ
227. istency and in practice many systems then need to introduce notions of compensation activities to undo changes that may have depended on a transaction that has now been cancelled For such compensation activities to be automated they need to be specified in advance for each transaction In the vast majority of cases the transaction is not cancelled and the compensation action is just discarded It has been estimated that up to 40 of DBMS activity relates to preparation of compensation actions that are never needed and complex cases have been described that require whole hierarchies of compensation actions Dependent systems should not take any consequential action until the database transaction is committed if this rule is followed there should be no need for compensation There are several reasons commonly given for not following the rules One hinted at above is that the transaction may involve third parties and the delays involved in using distributed commit protocols seem excessive This amounts to parties proceeding in the absence of agreement and must be seen as a risky step Another reason is that most DBMS using locking for transaction control and so parts of the database are locked during the distributed transaction protocol which can be costly This last point is really quite hard to understand since robust optimistic transaction protocols that minimise locking have been well documented for decades Pyrrho uses optimistic concur
228. it gt This is called an absolute URI URIs with common initial segments form XML namespaces For example we could have a namespace all of whose URIs begin with http abc com a We might define a shorthand to save us repeating this part In XML we can add an attribute of form xlmns a http abc com a and then an element with name a thing would be defined in the namespace at lt http abc com a thing gt Prefixes introduced in this way in XML take effect from the start of the element that contains such an attribute so the xlms attribute in this case might be in an element named a thing xmIns can be used to define or redefine the blank or default namespace 74 The Pyrrho Book May 2015 There are similar facilities for defining namespaces in SQL 8 2 OWL Types SQL2011 like SQL2003 differed from older DBMS s by having a stronger system of data types For example user defined types have methods and constructors and ordering functions can be declared Pyrrho has built on this system by including support for OWL types For convenience and best results IRIs identifying OWL types can be added to domain and type definitions e g the following is accepted as SQL by Pyrrho create domain watts as real units watt provided that units has been previously defined for example with Pyrrho s create xmInamespaces statement Adding an IRI in this way creates a subtype or subdomain of real in this case and informs Pyr
229. k 9 Ends with 9 Home Share lisation 6 Protocol byte Request DbStorage Flush complete for A _ 10 Protocol byte RemoteBegin 10 Protocol byte CloseConnection Exception 00000 10 Rollback 10 Ends with 9 6 Protocol byte RemoteCommit IStartCommit for _ osp at 974 DbStorage Flush complete for A _ osp len 6 Ends with 31 Home Share View O DATA E A LJ osp D osp lt 2 items p a Bs x e E DATA E gt B N difie LJ osp 5 _00127 0 0 1 5434 23 03 2015 15 D osp 23 03 2015 lt A commits its changes note A s _ is now 1175 bytes and deletes the temporary transaction record Press Enter twice 141 EN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 127 0 0 1 5 ntinue r to Continue to Continue 34 Enter to Continue 342 H to Continue Role D User Enter ialisation _ 127 0 0 1 Enter to Contin r to start 27 0 0 1 54 start _ 5 Enter to art Flush complete for B _ r _ 9 Enter to start Enter to Continue _ 127 4 6 Enter to Contin Enter to Continue 974 mplete for Enter to start mpl Enter to Continue osp at Continue 1 5434 6 Enter to Contin 974 0sp len 105 into E yrrhoCmd i t into sword The Pyrrho Book May 2015 Enter to Continue 127 0 0 1 5434 974 _ 127 0 0 1 5435 974 0sp len 105 _ 9 Enter to
230. k May 2015 e g Kung and Robinson 1981 So in both cases transaction failure can result from conflict for pessimistic control it is a conflict of intention while for optimistic control it is a conflict of action Optimistic Concurrency Control OCC is not widely used in commercial DBMS products Although it always produces serialisable transaction behaviour there is no way of guaranteeing in advance that any given transaction will be able to commit With pessimistic concurrency control PCC a transaction is allowed to delay starting until it has succeeded in locking the data it wishes to read or write and these locks are maintained by the DBMS until the end of the transaction that owns them PCC is subject to denial of service attacks since an attacker can repeatedly request locks on a large set of data items thus delaying legitimate transactions Such an attack might leave few traces since the delay will occur even if the attacker s transaction makes no changes and simply times out In widely distributed information systems made possible by the Internet the impossibility of maintaining database locking while a user organises their payment methods has led many to abandon the use of ACID databases altogether Lessner et al 2012 Where locking processes have been combined with such distributed transactions it has been found necessary to introduce the idea of compensation processes effectively to automate the cancelling of supposedly d
231. l except that customer address information is only visible to the Clerk and Deliveryman Individuals might be allowed to adopt more than one role but it should always be clear what role they are currently in So if John the Clerk is temporarily allowed to do something in the Manager s absence we should be able to look back to see what he did in that role Example For example suppose a small sporting club such as squash or tennis wishes to allow members to record their matches for ranking purposes E Members id int primary key firstname char Played id int primary key winner int references members loser int references members agreed boolean For simplicity we give everyone select access to both these tables Grant select on members to public Grant select on played to public Although Pyrrho records which user makes changes it will save time if users are not allowed to make arbitrary changes to the Played table Instead we will have procedure Claim won beat and Agree id so that the Agree procedure is effective only when executed by the loser With some simple assumptions on user names the two procedures could be as simple as Create procedure claim won int beat int insert into played winner loser values claim won claim beat 53 The Pyrrho Book May 2015 Create procedure agree p int update played set agreed true where winner agree p and loser in select m id from member
232. l of the grant options So the single SQL statement has been expanded into three Grant records in the database 586 as we can see refers to the Librarian Generally log entries refer to database objects by number rather than by name Pyrrho has always done this because objects can be renamed The mechanism now works really well for role based naming so that the new version is backwards compatible with existing Pyrrho databases The second extract is the last few entries in the log from 878 on where the user is Fred T Here the user is Fred and the role is LIBRARIAN The transactions correspond to the four SQL statements 68 The Pyrrho Book May 2015 alter table book add Available boolean default true create role reader grant select Title Author Available on book to reader grant reader to public The Grant NoPrivilege entry is probably not required but at present it ensures that table BOOK 197 is entered in the namespace for READER 970 One other oddity in this list is where the Avaialble column is defined The figures 197 4 895 are for the table BOOK the table s owner and the new column s domain whichis a slightly odd collection of data to display in the Log entry the table s owner is not actually mentioned in the log entry 7 2 Legacy Data When importing tables from an existing database it is good to take the opportunity for some minor redesign For example additional int
233. l possible to see if extra lines have been output to these windows Now open a file browser and change directory to the A folder We will use this window to check folder contents as we go along In the screenshots show all three folders A B and C All should be empty at this stage C is out of sight in the above screenshot In the command window create a new database called D by giving the command PyrrhoCmd p 5434 D Notice the SQL gt prompt in the terminal window Although this command implies that a new database D osp will be created nothing is actually written to disk until the first change is committed Ba E O x EN Command Prompt PyrrhoCmd p 5434 D t E DATA E gt A This folder is empty 123 The Pyrrho Book May 2015 At the SQL gt prompt give the command create table E F int primary key Notice the creation of D osp in the folder browser DA aa Xx EM Command Prompt PyrrhoCmd p 5434 D H DATA E A At the SQL gt prompt give the commands insert into E values 4 7 table E Verify that we have two rows in table E Ba fant O x EN Command Prompt PyrrhoCmd p 5434 D F DATA E A 1 item m The command table Sys Table also gives a way of reporting on tables in the local database Here it reports that E has one column and two rows Also look at table Log and close the session with C You can leave the command window open Tle
234. la z x EX Command Prompt i x Fite Home Share View E DATA E A Name _ D osp 1 item ye E DATA E B Date modified Type items Before we go on we note that this is exactly how normal databases work if we insert 2 rows we see 2 rows If we create no tables we see no tables etc In the very next step we will see some very different but still correct behaviour 124 The Pyrrho Book May 2015 A4 3 Configure a storage replica of the sample database In the command window create a configuration database whose name is _ for server B PyrrhoCmd p 5435 _ At the SQL gt prompt give the command on a single line or enclosed in insert into _Database values D 127 0 0 1 5435 4 password 127 0 0 1 5434 Student password This looks as if it shouldn t work since we have not created a table called Database But Pyrrho treats the configuration database in lots of special ways In the file browser we can see that we now have a database called _ osp in the B folder This is as expected However we see that Pyrrho has also created D osp in B and _ osp in A Bl IA a x EX Command Prompt PyrrhoCmd p 5435 _ x Fite Home Share View 0 3 F t H DATA E gt A Name De Osp D osp lt gt 2 items E Os El x o t D DATA E gt B Name Date modified Osp _ D osp lt gt 2 items ES Moreover
235. level 4 class and there is one per base table accessed during T see section 3 8 1 The ReadConstraint records e The local transaction T e The table concerned e The constraint CheckUpdate or its subclasses CheckSpecific BlockUpdate CheckUpdate records a list of columns that accessed in the transaction CheckSpecific also records a set of specific records that have been accessed in the transaction If all records have been accessed explicitly or implicitly by means of aggregation or join then BlockUpdate is used instead ReadConstraints are applied during query processing by code in the From class The ReadConstraint will conflict with an update or deletion to a record R in the table concerned if e the constraint is a BlockUpdate or e the constraint is a CheckSpecific and R is one of the specific rows listed This test is applied by LocalTransaction check Physical p which is called from Commit1 Entity Integrity The main entity integrity mechanism is contained in LocalTransaction However a final check needs to be made at transaction commit in case a concurrent transaction has done something that violates entity integrity If so the error condition that is raised is transaction conflict rather than the usual 51 The Pyrrho Book May 2015 entity integrity message since there is no way that the transaction could have detected and avoided the problem Concurrency control for entity integrity constraints are handled by Ind
236. license from the University of the West of Scotland 1 2 The Pyrrho DBMS server The server PyrrhoSvr exe is normally placed in the folder that will also contain the database files The Professional and Open Source editions of PyrrhoSvr can be started from the command line by the user who owns this folder It is a good idea to run the server in a command window because occasionally this window is used for diagnostic output If you are using Embedded Pyrrho only the database engine is included in the application and so the server does not need to be running Pyrrho provides its client service by default on port 5433 but will find another port if 5433 is already in use By default Pyrrho will try to set up a REST service on ports http 8180 and https 8133 using Windows authentication and a MongoDB like service on port 27017 You can supply your own server certificate for transport layer security and or specify different ports On Windows 7 systems and later if you get Access denied you can either run the server as administrator or you can fix the http url reservations To do this open a command prompt as administrator and issue the following commands with your full user name where shown netsh http add urlacl http 127 0 0 1 8180 user DOMAIN user netsh http add urlacl https 127 0 0 1 8133 user DOMAIN user If you get other error messages try using different ports using the command line options described below 1
237. lient the client user s name will be recorded in the very first record of the file this user is then established as the database owner and by default has full administrative control over the database On the Open Source edition of Pyrrho database files have extension osp For other editions the extension is pfl For example a database called Sales will be contained in a file Sales pfl or Sales osp If a database file grows beyond 4GB it will be split into sections after the first one their names will be Sales 1 pfl or Sales 1 osp etc As is suggested by the different extensions Open Source Pyrrho files cannot be used by other editions and vice versa You can inspect the database folder from time to time to check everything is in order It is not a good idea to rename a database file as that is the name of the default database Role and Pyrrho will infer some sort of partitioning if the two do not match For embedded applications the database file s should be installed alongside the application e g as an asset 1 5 The client programs There are two client utilities at present a traditional command line interpreter PyrrhoCmd and a Windows client called PyrrhoSQL As with all Pyrrho clients the PyrrhoLink dll or OSPLink dll assembly is also required We discuss these first The distribution also contains a REST client and a transaction profiling utility OSPLink dll or the Java package org pyrrhodb is used by any applicat
238. ll see later that we can have expressions whose values changes as an enumerator advances These are obviously not constant and so if the Key value supplied to GetRowEnumerator was such a value while it would still be true that in each case there is either one or zero matching pairs in the tree we need to reset and re enumerate the tree to find out which On the other hand it is such an important optimisation to be able to replace an enumerator with a trivial or empty enumerator that it seems worth adding some machinery to the database engine to keep track of which expressions are constant This is done using the extension method IsConstant the static class defining this is called Varies in the Common cs source file Note that even long values might not be constant a long value might be a record number or defining address which will advance during an enumeration ATree lt K V gt Subclasses The ATree class provides the basic tree implementation that is used by all the tree types in the DBMS It also provides a standard mechanism for enumerating the Keys and Values of a tree which allows the use of C s foreach statement for Slots Keys and Values Other implementations provide special actions on insert and delete e g tidying up empty nodes in a multilevel index The main implementation work is shared between the abstract ATree lt K V gt and Bucket lt K V gt classes and their immediate subclasses There are just 5 ATree implementati
239. lues lt 2 items B T DATA E gt B Name Date modified osp D osp 23 03 lt 2 items c e T DATA E C Do Enter once in B s window and a few ties in C s and note the GetMaster request from C to B EN Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S fH Command Prompt OSP T d C p 5436 s 0 S 0 M 0 Closed D 9 Enter to Continue Phase 3 for D 10 Enter to start Phase 4 for D 10 Enter to start 12 Protocol byte CloseConnection Connecting D 9 127 0 0 1 5435 Exception 00000 About to Begin D 9 Enter to Continue 12 Rollback Closed D 9 Enter to Continue About to Close D 15 Enter to Continue 5 tid 3 Committed Ficlosed D 15 Enter to Continue 5 Protocol byte ExecuteReader 12 Ends with 9 Connecting D 9 127 0 0 1 5435 Connection 14 Coordinator 127 0 0 1 5436 labout to Begin D 9 Enter to Continue Connecting D 17 127 0 0 1 5434 Connecting D 10 127 0 0 1 5435 About to Begin D 17 Enter to Continue About to Begin D 10 Enter to Continue 14 Protocol byte RemoteBegin 5 Coordinating Commit for tid 4 Flconnection 16 Coordinator 127 0 0 1 5436 RemoteTransaction D Connecting D 19 127 0 0 1 5434 Phase 1 for D 11 Enter to start Flabout to Begin D 19 Enter to Continue prepare sending GetMaster for D 16 Protocol byte RemoteBegin gt Master F 16 Protocol byte GetMaster Begin and Connecting D 127 0 0 1 5434 11 127 0 0 About to B
240. main accessible SQL gt C E OSP gt PyrrhoCmd p 5434 _ SQL gt Delete from _Partition 1 records affected SQL gt aC E OSP gt PyrrhoCmd p 5434 D SQL gt table E SQL gt AC E OSP gt PyrrhoCmd p 5435 D2 SQL gt table E 168 The Pyrrho Book May 2015 The following steps during setting up the partition can be observed by using the T Tutorial flag on both servers Stop the servers clear the folders A and B and repeat steps 1 to 3 but add the T flag when starting the servers EX Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EN Command Prompt OSP T p 5435 d B s 0 S 0 M 0 IE OSP gt OSP p 5434 d A s 5 0 M 0 OSP gt 0SP d B s 0 p 5434 d MA s S M 0 Enter to start up Pyrrho DBMS c 2015 Malcolm Crowe and University of a C and University of the West of Scotland 2 27 March 2015 www pyrrhodb com rrhoDBMS protocol on 127 0 0 1 5434 Database folder A nc IE OSP gt OSP T p 5434 d A s 5 0 M 0 T p 5434 d A s S M 0 Enter to start up P i of the West of 2 27 March 2015 www pyrrhodb com PyrrhoDBMS protocol on 127 0 0 1 5434 Database folder A When you repeat step 3 now server A will pause waiting for you to confirm the first step of the transaction commit process the reason for this will become a little clearer below PyrrhoCmd p 5434 D create table E F int G char primary key F G EN Command Prompt OSP T p 5434 d
241. mand Prompt OSP T d B p 5435 s 0 S 0 M 0 EN Command Prompt osp T p 5434 d A s 0 5 0 M 0 Reconfigure _ Phase 1 for _ 7 Enter to start Phase 1 5 for _ 7 Enter to start Phase 2 for _ 7 Enter to start Phase 3 for _ 7 Enter to start StartCommit for _ osp at 34 DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 7 Enter to start 7 tid 4 Committed 5 Protocol byte RemoteBegin 5 Protocol byte IndexLookup 5 Protocol byte IndexNext 5 Protocol byte IndexLookup 5 Protocol byte IndexNext 3 Protocol byte CloseConnection ontinue fl ta X EN Command Prompt PyrrhoCmd p 5435_ x The closing of the connection for D on both servers is acknowldged byserver A Exception 0000 Rollback is the normal ending for a transaction that makes no changes B now wants to make the configuration changes to _ Press Enter Command Prompt osp T p 5434 d A s 0 S 0 M 0 Command Prompt OSP T d B p 5435 s 0 S 0 M 0 Reconfigure _ Phase 1 for _ 7 Enter to start Phase 1 5 for _ 7 Enter to start Phase 2 for _ 7 Enter to start Phase 3 for _ 7 Enter to start iStartCommit for _ osp at 34 DbStorage Flush complete for A _ osp len 979 Phase 4 for _ 7 Enter to start A Ka 7 tid 4 Committed n es 3 d pe p len 979 5 Protocol byte RemoteBegin 5 Protocol byte IndexLookup 5 Protocol byte IndexNext 5 Protocol byte IndexLookup 5 Protocol byte In
242. md window the temporary files have been removed and the B server needs to finish its read only transaction press Enter twice in the B server window Command Prompt osp T p 5434 d A s 0 S 0 M_ i Command Prompt OSP T d B p 5435 sil E Command Prompt OSP T d C p 5436 s 0 S 0 M 0 4 Protocol byte CheckSerialisation Phase 2 for _ 5 Enter to start 4 Protocol byte CheckSerialisation DbStorage Flush complete for C _ 127 0 0 1 5435 1137 127 4 Protocol byte Request Phase 2 for _ 9 Enter to start DbStorage Flush complete for B _ _ 124qhout to Request _ 127 0 1 5435 6 Enter to Continue Connection 6 Coordinator 127 0 0 1 5434phase 3 for _ 5 Enter to start Connecting D 9 127 0 0 1 5434 onnecting D 5 127 0 0 1 5435 gAbout to Begin D 9 Enter to Continue lapout to Begin D 5 Enter to Continue 6 Protocol byte RemoteBegin tartCommit for _ osp at 974 4 Protocol byte RemoteCommit DbStorage Flush complete for C _ osp len 1142 ptartComit for _ osp at 1137 Phase 3 for D 7 Enter to start DbStorage Flush complete for B _ osp Ippase 3 for _ 9 Enter to start 4 Ends with 31 2 About to Commit _ 127 0 0 1 5435 6 Enter to Continue 6 Protocol byte CloseConnection Closed _ 127 0 0 1 5435 6 Enter to Continue Phase 4 for _ 5 Enter to start s Phase 4 for D 7 Enter to start About to Close D 9 Enter to Continue Closed D 5 Enter to Continue Closed D 9 Enter to Continue Phase 4 for _ 9 Enter to start 6 Ends
243. ment and also groups profiles with similar pattern for example where everything is the same apart from the number of affected rows The Distributed Database and Partitioned tutorial in Appendices 4 and 5 demonstrate how Pyrrho uses three phase commit for distributed transactions At this point in this book it seems a good point to state once again that while Pyrrho uses optimistic concurrency control it is totally transaction safe If you are using explicit transactions you can use the system LogS table to view the proposed changes for the current transaction Each connection will have its own and it is easy to see the they are isolated the only entries with known positions are the ones that predated the start of the transaction Ex Command Prompt pyrrhocmd h2 O Accordingly the transaction commit protocol is in 4 or 5 phases controlled by locks on the transaction log file which in Pyrrho is the durable version of the database 1 Verify the transaction does not 50 The Pyrrho Book May 2015 conflict with anything written since the start of the transaction 1 5 Lock the database and repeat this test 2 Prepare the binary package to be written 3 Write it to the disk file and unlock the database 4 Now discard the local transaction and allow the client to see the database as it now is If multiple servers or databases are active then step 3 here requires three phase commit during which time the proposed changes are written to tem
244. n enclose the input i e be the first and last non blank characters in the input SQL gt create table directors id int primary key gt surname char gt firstname char pic blob Note that continuation lines are prompted for with gt It is okay to enclose a one line statement in Note that Pyrrho creates variable length data fields if the length information is missing as here This seems strange at first a field defined as CHAR is actually a string Binary data is actually stored inside the database table and in SQL such data is inserted using hex encoding But PyrrhoCmd supports a special syntax that uses a filename as a value SQL gt insert into directors id surname firstname values 1 Spielberg Steven spielberg gif The above example shows how PyrrhoCmd allows the syntax source as an alternative to the SQL2011 binary large object syntax X 474946 PyrrhoCmd searches for the file in the current folder and embeds the data into the SQL statement before the statement is sent to the server As this behaviour may not be what users expect the first time Pyrrho uploads or downloads a blob a message is written to the console e g Note the contents of source is being copied as a blob to the server source can be enclosed in single or double quotes and may be a URL i e source can be http something Another use of file for importing datafrom spreadsheets is described in appendix 3
245. n CUSTNAME for 71 2 134 Pcolumn3 220 55 247 Check SUFFICIENT_FUNDS 71 balance gt 0 Pcheck 71 55 284 PTransaction for 1 Role 4 User 32 Time 10 02 2013 16 27 15 PTransaction 0 0 300 Record for 71 152 101 INTEGER 195 456 78 NUMERIC pS tg S 2 220 Fred CHAR Record 300 284 334 PTransaction for 1 Role 4 User 32 Time 10 02 2013 16 2 PTransaction 0 0 350 Record for 71 152 103 INTEGER 195 682 91 NORTE p B S 2 220 Joe CHAR Record 350 334 SQL gt Pyrrho identifies everything in the database by its defining position Pos When the database is first created a default Schema role and the owner are recorded here at Pos 4 and 32 These are the only records that do not have transaction information Then we see 3 transactions corresponding to the three SQL commands issued so far Each transaction records the use the role and the timestamp The last two transactions are the Insert statements of type Record The first transaction defines the accounts table and you can see the steps involved in setting up the three domains and the three columns The Log table is one of a great many system tables that allow the SQL engine to examine the database history There are tables whose names begin with Log that are a historical record while the system tables beginning with Sys or Role show the current database objects 7 The idea that all internals of the database engine should be exposed in relational tables is a conseque
246. n number of the currently committed data 47 The Pyrrho Book May 2015 e If the version numbers are the same then no one else changed the record and the system can write the updated value e f the originally read value and the current value on the disk are not the same then someone has changed the data since it was read and the current operation is probably out of date Thus the system discards the version of the data aborts the transaction and returns an error message e The step of checking the version numbers is called validation The validation can be performed at the commit time normal validation or at the time of writing each statement early validation In solidDB early validation is the default method General TransactionEarlyValidate yes Each time a record is updated the version number is updated as well Each user s transaction sees the database as it was at the time that the transaction started This way the data that each user sees is consistent throughout the transaction and users are able to concurrently access the database Even though the optimistic concurrency control mechanism is sometimes called optimistic locking it is not a true locking scheme the system does not place any locks when optimistic concurrency control is used The term locking is used because optimistic concurrency control serves the same purpose as pessimistic locking by preventing overlapping updates When you use optimistic locking you do
247. n object The transaction has been rolled back SQL gt ROLLBACK There is no current transaction 101 1000 202 12000 SQL gt BEGIN TRANSACTION SQL T gt SELECT BankTransfer 101 202 100 FROM DUAL SQL T gt SELECT FROM Accounts Internal error Object reference not set to an instance of an object The transaction has been rolled back SQL gt BEGIN TRANSACTION SQL T gt SELECT BankTransfer 100 202 100 FROM DUAL The Pyrrho Book May 2015 SOL T gt SELECT FROM Accounts Internal error Object reference not set to an instance of an object The transaction has been rolled back SOL gt SELECT FROM Accounts 101 1000 202 12000 SQL gt BEGIN TRANSACTION SQL T gt SELECT BankTransfer 101 200 100 FROM DUAL SQL T gt SELECT FROM Accounts Internal error Object reference not set to an instance of an object The transaction has been rolled back SQL gt SELECT FROM Accounts 101 1000 202 12000 SQL gt BEGIN TRANSACTION SQL T gt SELECT BankTransfer 101 202 2000 FROM DUAL SQL T gt SELECT FROM Accounts Internal error Object reference not set to an instance of an object The transaction has been rolled back SQL gt SELECT FROM Accounts 1
248. n restored to an earlier time On the other hand in a world of distributed transactions there might be historical dependencies that no longer matter Suppose originally database A was constructed on the basis of data in B to the extent that updates to a table T were part of a distributed transaction that involved B Does this mean that A cannot survive the destruction of B Would it matter if T is dropped from A The fact that A no longer cares about database B needs to be configured in the local information about A Certainly it makes for an unpractical situation if we cannot draw a line and say take the contents of this table as given and don t enquire where it came from After all if a table is built by an application that has several connections open then the DBMS will have no knowledge about the transactional dependency Just because we used a multi database connection and SQL to create T need not create a database dependency 86 The Pyrrho Book May 2015 9 6 Cooperating Servers In this new design obviously there is no central point of control we regard domain user names and authentication as someone else s problem and Pyrrho servers work co operatively to provide support for distributed data of various kinds By default a Pyrrho server will start by trusting the account that started it up and the machine it is running on It will load the configuration database if present that tells it what its role is if this database
249. nString Files Temp conn gt Open rdr conn gt Execute table a row rdr gt Read while is_int row print row row 1 r n row rdr gt Read a Now at a command prompt try php try php Relational Database Implementation 106 The Pyrrho Book May 2015 Appendix 2 The Transactions mystery tour I ve included this as an appendix because I found it a genuinely astonishing experience to work with Martti Laiho on this DBTech tutorial see www DBTEchNet org We never really finished it but it led me to make a number of changes I ve included the complete text of the tutorial as published Don t enter the text in blue though as it s either comments or specific to the Linux version they were using DBTechNet DBTech VET Martti Laiho 2012 12 19 SQL Transactions Appendix 1 Pyrrho Welcome to the Transaction Mystery Tour using Pyrrho DBMS Following experiments with the Pyrrho transactions can be tested using the free DebianDB database laboratory of DBTechNet or on Windows e a n On Li x S gt Sssea sSasesHsSe For the first steps on using Pyrrho in DebianDB see the Quick Start Guide at http www dbtechnet org download QuickStartToDebianDBv05 pdf Downloading OSP zip from http pyrrhodb uws ac uk OSP zip and unzipping it as root debianDB home student Downloads unzip Z OSP zip d opt Login as student Studentl To start the Pyrrho server enter
250. nce between say a table with certain columns a multiset of rows with similarly named fields and a multiset of a structured type with similarly named attributes even though in an element of each of these the value of a column field or attribute respectively is referenced by syntax of the form a b Some constructs within SQL2011 overcome these differences for example the INSERT statement uses a set of values of a compatible row type to insert data into a table and TABLE v constructs a table out of a multiset v The type model in Pyrrho allows user defined types to be simple or structured they can define XML data types e g for RDF OWL use have an associated URI and constraints To use structured types it is necessary to CREATE TYPE for the structured type this indicates the attributes and methods that instances of the type will have Then a table for example can be defined that has a column whose vales belong to this type At this stage the table could even be populated since there is an implicit constructor for any structured type but before any methods can be invoked they need to be given bodies using the CREATE METHOD construct Note that you cannot have a type with the same name as a table or a domain since a type has features of both Values of a structured type can be created using a constructor function assigned to variables used as parameters to suitably declared routines used as the source of methods and placed in suitably
251. nce of Codd s 1985 principles Since Pyrrho s transaction logs are durable all their details are exposed in system tables See Appendix 8 25 The Pyrrho Book May 2015 A particularly useful one is RoleSTable SQL gt table Role Table Pos Name Columns Rows Triggers checkconstraints References RowIri Oowner Tee e ooss ossoo A E aa 71 ACCOUNTS 3 12 10 11 10 Bank SQL gt This records the current name of table 71 as ACCOUNTS and shows it currently has 2 rows Note that the script we used for creating the table was all in lower case The SQL standard says that unquoted identifiers are not case sensitive If you want case sensitivity or special characters you need to double quote the identifier as we did with Logs There are some notes on this aspect of the design of Pyrrho DBMS at the end of this chapter Example 2 C application Let us write a simple application that uses this database This one uses Windows Forms for simplicity To create it from scratch start up Visual account Fred Studio and select New Project gt Visual C gt Windows gt WPF Application aen Add a Reference to PyrrhoLink dll J Pay In Pay Out Add user interface elements as shown I used a StackPanel instead of a 50678 Grid for the main window and used horizontal and vertical StackPanels Source for the detail of
252. nd partitions and new DDL for databases only For master and storage databases the set of objects may be limited for example for a storage database the system tables will be mostly empty although the log tables will be available This is useful for forensic examination of data files crash analyses etc since log data can still be filtered joined between databases etc 7 When atransaction finally commits both the connecteddatabase and global database lists are updated with the new versions of the databases involved and the changes are loaded 8 A localtransaction for the configuration database is rather special when the transaction is about to commit the proposed changes are examined to see which ones affect other servers If there are any such the other server configuration databases are added to the transaction with the consequential changes for them If the changes involve configuring partitions any data moves are added to the distributed transaction 9 When the transaction finally commits all databases where the server role has changed must be reloaded 9 5 Database Dependency If we need multi database transactions for example between a local database and a remote one then we will create dependencies between them Just because a database is remote doesn t mean we don t own it So we should generally check that the relationship between them makes sense and that one of the participants to a distributed transaction has not bee
253. nerationRule ADD DROP Metadata When columns are renamed Pyrrho cascades the change to SQL referring to the columns AlterType TO id ADD Member Method DROP Member_id Routine Representation DROP Metadata ALTER Member_id AlterMember Other details of a Method can be changed with the ALTER METHOD statement see Alter above Member id Type DEFAULT Value Collate AlterMember TO id DROP Metadata TYPE Type SET DEFAULT Value DROP DEFAULT SET SOURCE TO QueryExpression TO id AlterView SET INSERT UPDATE DELETE TO SqlStatement ADD DROP Metadata Metadata ATTRIBUTE CAPTION ENTITY HISTOGRAM LEGEND LINE POINTS PIE X Y CAPPED USEPOWEROF2SIZES BACKGROUND DROPDUPS SPARSE MAX int SIZE int string iri The Metadata flags and the string constraint are Pyrrho extensions Attribute and Entity affect XML output in the role Histogram Legend Line Points Pie for table view or function metadata Caption X and Y for column or subobject metadata affect HTML output in the role HTML responses will have JavaScript added to draw the data visualisations specified Other metadata keywords are for MongoDB The string is for a description and for X and Y columns is used to label the axes of charts If the table s description string begins with a lt it will be included in the HTML so that it can supply CS
254. nfigure _ Exception 00000 Connection 2 Coordinator 127 0 0 1 5434phase 1 for _ 4 Enter to start 2 Rollback Connecting D 5 127 0 0 1 5434 a 106 tari tab cater talstert 2 Ends with 9 bout to Begin D 5 Enter to Continue Phase 2 for 4 Enter to start Connection 4 Coordinato 27 0 0 1 5435 Files Phase 3 for 4 Enter to start StartCommit for _ osp at 34 DbStorage Flush complete for Phase 4 for _ 4 Enter to sta 3 tid 2 Committed Connecting D 5 127 0 0 1 54 DbStorage Flush complete for C osp len 39 Share View NOSP gt PyrrhoCmd p 5436 _ insert into _Database values D 2 password 127 0 0 1 5435 student DATA E gt ssword We recall that the insert statement has configured a query service for D on C to obtain its data from server B We see that server C has just connected to D on B and B has synchronised with D s master server A To move things along we need to press Enter in the B server window E Command Prompt osp T p 5434 d A s 0 S 0 E Command Prompt OSP T d B p 5435 s 0 S Command Prompt OSP T d C p 5436 s 0 S 0 M 0 StartCommit for _ osp at 974 Closed _ 127 0 0 1 5434 6 Enter A DBMS c 2015 Malcolm Crowe and University of the Wes bStorage Flush complete for A _ osp len Phase 4 for _ 5 Enter to start 5 2 19 March 2015 www pyrrhodb 6 Ends with 31 Phase 4 for D 7 Enter to start PyrrhoDBMS protocol on 127 0 1 5436 Phase 4 for _ 9 Enter to start a
255. ng folder Sc A Database A PTest S Table MEMBERS Recs 1 Dels 0 Spec 0 Blocked False Record Occurs 1 ID MNAME CREDIT 5 Profile Trans 15 Fails 12 Load Fetch 5 Pattem 3 Transaction 1 Tables 1 Occurred 15 Failed 12 S Table MEMBERS Recs Dels 0 Spec 0 Blocked True Record Occurs CREDIT 4 Transactions 5 Profile Trans 44 Fails 0 5 Pattem 3 Transaction 4 Tables 1 Occurred 44 Failed 0 10 09 2010 13 43 58 159 transactions 8 Table MEMBERS Recs Dels 0 Spec 2 Blocked False Transactions 5 Transaction 4 Tables 1 Occurred 24 Failed 0 4 Table MEMBERS Recs 1 Dels 0 Spec 2 Blocked False 5 Transaction 8 Tables 1 Occurred 20 Failed 0 Table MEMBERS Recs 2 Dels 0 Spec 2 Blocked False Profiling has a negligible effect on performance and memory use Profiling can be enabled for all databases or in the configuration of individual databases The purpose of gathering or storing profile information is to understand and monitor the causes of transaction conflicts Performance tuning and database design should seek to minimise failed transactions during normal operation It is inevitable that an unusual operation such as changing the schema or making an update affecting all rows of a table will be hard to commit during heavy traffic because a conflicting transaction will probably occur in the meantime When profiling is turned off or on for a database called name profiling information is destructively
256. ngs on the server side for example with the SQL ORDER BY clause will need to be informed about the locale context for the strings being sorted The SQL standard assumes that the collation to use is defined for each table or within a given SQL statement or expression In designing localised applications programmers need to select the right combination of server side settings to give an entirely satisfactory localised experience At the server side views and updatable generated columns provide opportunities for localisation which can be targeted by defining roles for specific locales With the help of the role based models in Chapter 7 a role with the Chinese locale for example could see Chinese names for tables and columns and there could be role specific generated always columns that defined Chinese versions of informative messages for a user application The localised version of the application would then attach to the appropriate role and use the appropriate column to get the localised resources for the application This could be a very powerful tool to add to the localisation mechanisms available in ASP NET for example There are evident gaps in this provision For example it could be a property of a role to set the locale so that the collations used for ordering string data are set by default to match the role s locale 8 7 Using structured types Structured types multisets and arrays can be stored in tables There is a differe
257. niversity of the West 5 2 19 March 2015 www pyrrhodb com 5 2 19 March 2015 www pyrrhodb com Connecting D 3 127 0 0 1 5434 byrrhoDBMS protocol on 127 0 0 1 5436 About to Begin D 3 Enter to Continue Database folder C sClosed D 3 Enter to Continue Connection 1 Files _ User PyrrhoDBMS protocol on 127 0 0 1 5435 a ction Database folder B lA ow O x EX Command Prompt PyrrhoCmd p 5436 _ x Home Share View T DATA E A A Name SQL gt insert into _Database values D 127 0 0 1 5436 2 password 127 0 0 1 5435 student password E Command Prompt osp T p 5434 d A s 0 S 0 M BN Command Prompt OSP T d B p 5435 sit y Command Prompt OSP T d C p 5436 s 0 S 0 M 0 36 s 0 S 0 M 0 0 S 0 i 5 M 0 Enter to start up Pyrrho DBMS c 2015 Malcolm Crowe and Pyrrho DBMS c 2015 Malcolm Crowe and University of the Mel 5 2 19 March 2015 www pyrrhodb com 52 19 March 2015 www pyrrhodb com Connecting D 3 127 0 0 1 5434 PyrrhoDBMS protocol on 127 0 0 1 5436 About to Begin D 3 Enter to Continue batabase folder C Closed D 3 Enter to Continue Connection 1 Files _ User PyrrhoDBMS protocol on 127 0 0 1 5435 1 Protocol byte ExecuteReader Database folder MBA DbStorage Flush complete for C _ osp len 39 3 Coordinating Commit for tid 2 Reconfigure _ Phase 1 for _ 4 Enter to start ow lA 1 DATA E A
258. nnection string and connection inside the class as we did for MySQL string str SqiCeConnection conn In the MainWindow method give the value of the connection string you found above the tells C not to interpret as an escape character and open the connection str Data Source C Temp clubWPF Database1 sdf conn new SqlCeConnection str conn Open In the Grid_Loaded_1 method give the following code var cmd conn CreateCommand cmd CommandText select from Member var rdr cmd ExecuteReader members Children Clear var nr 0 while rdr Read var rd new RowDefinition rd Height new GridLength 1 GridUnitType Auto 99 The Pyrrho Book May 2015 members RowDefinitions Add rd for int j 0 j lt 3 j AddBox rdr nr j nr and add a new method to the class void AddBox IDataReader r int nr int nc var tx new TextBox tx Text r nc ToString members Children Add tx Grid SetRow tx nr Grid SetColumn tx nc WPF allows you very tight control over appearance of everything and is very fast To make changes to the database with ADO NET you can do something like cmd CommandText insert into member values 92 Joe Soap cmd ExecuteNonQuery So modify the xaml to provide some extra textboxes and buttons wrapping these and the Grid with a StackPanel something like FILE EDIT VIEW PROJECT BUILD DEBUG TEAM SQL DESIGN FORM
259. nown from account CAST toAcct AS VARCHAR 10 ELSE SET msg OK END IF END END IF RETURN msg toAcct CAST toAcct AS VARCHAR 10 amount CAST amount AS VARCHAR 10 END COMMIT BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES 101 1000 INSERT INTO Accounts acctID balance VALUES 202 2000 SELECT FROM Accounts COMMIT BEGIN TRANSACTION SELECT BankTransfer 101 202 100 FROM DUAL SELECT FROM Accounts ROLLBACK 115 The Pyrrho Book May 2015 BEGIN TRANSACTION SELECT BankTransfer 100 202 100 FROM DUAL SELECT FROM Accounts ROLLBACK BEGIN TRANSACTION SELECT BankTransfer 101 200 100 FROM DUAL SELECT FROM Accounts ROLLBACK EGIN TRANSACTION ELECT BankTransfer 101 202 2000 FROM DUAL ELECT FROM Accounts ROLLBACK SQL gt BEGIN TRANSACTION SQL T gt DELETE FROM Accounts SQL T gt INSERT INTO Accounts acctID balance VALUES 101 1000 I SQL T gt INSERT INTO Accounts acctID balance VALUES 202 2000 SQL T gt SELECT FROM Accounts 101 1000 202 12000 SQL T gt COMMIT SQL gt BEGIN TRANSACTION SQL T gt SELECT BankTransfer 101 202 100 FROM DUAL SOL T gt SELECT FROM Accounts Internal error Object reference not set to an instance of a
260. ns EmbeddedPyrrho dll OSP dll where an application has one or more private databases It is very important to understand that the open source tools cannot be used with the professional server and vice versa The open source edition includes some database features omitted from the professional edition for reasons of security The open source client OSPLink dll supports SWI Prolog and PHP Otherwise the client API is compatible between the two editions In the Open Source Edition there is also a client library for Java OSPJ provides the package org pyrrhodb There are also some technical explanations of Pyrrho s inner workings in a document called Sourcelntro docx and there is a catalogue of the CH classes used in the server in Classes xlsx You are allowed to view and test the code and incorporate it in other software provided you do not create a competing product You can redistribute any of the files available on the Pyrrho website in their entirety or embed the dlls or any of the source code in an application Otherwise like other editions of Pyrrho use of this open source edition is subject to the end user license and any uses other than those described here requires a license from the University of the West of Scotland Database files are generally smaller than those of other database products Files do not contain any indexes or empty space so an empty database file is less than 1KB Database files do grow larger if there are many
261. nt database tables have been installed in the application for example using the sources provided by the RoleSClass system table sec 8 4 1 These methods use NET Reflection machinery to access public fields in the supplied object If you add other fields and properties to these classes do not make them public e g make them internal A9 7 PyrrhoDocument PyrrhoConnect Get Post Put Delete can be used for whole Documents and BSON Json and XML formats are supported This class can be used to access fields within Documents and to convert to and from Json and XML Note this class remembers the connection to the database if any and all these changes are transacted in the database unless the Document is detached or the connection is closed Method or Property Explanation PyrrhoDocument byte Constructor the binary data should be BSON PyrrhoDocument string Constructor the string should be Json or XML object this string Access a field of the document void Add string object Add or update a field to a Document void Attach string Attach the document to the given relative url in the database void Detach Forget the connection from this document to the database void Remove string Remove a field from a document string ToString Convert a document to Json byte ToBytes Convert a document to BSON String ToXML Convert a document to XML A9 8 Pyrrholnterval The methods and properties of Pyrrholnterval are Method o
262. nter to Continue losed _ 127 0 0 1 5435 14 Enter to Continue Phase 4 for _ 12 Enter to start p len 1163 hase 4 for D 13 Enter to start Phase 4 for D2 15 Enter to start 434 _ Bl lA Xx EN Command Prompt PyrrhoCmd p 5 Home Share View E DATA gt A assword 2 items LJ D2 osp Osp 30 03 20 Two more Enters and everything is done and we get the SQL gt prompt in the command window 177 The Pyrrho Book May 2015 EX Command Prompt OSP T p 5434 d A s 0 S 0 M 0 na X 5 dAB s 0 5 0 M 0 Enter to start len 1204 rtCommit for D osp at 24 Flush complete A D osp len Enter to start 3 Enter to Continue er to Continue _ 17 Enter to start Committed Diela X EM Command Prompt PyrrhoCmd p 5434 _ Fie Home Share View t E DATA E gt A Name 0sp LJ D osp lt 2 items D2 osp osp Close the session with C 7 Ends with 1 on A s window Now check that we have a record in the partition on D2 PyrrhoCmd p 5435 D2 table Sys Table needs Enters in both server windows 178 The Pyrrho Book May 2015 EX Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EM Command Prompt OSP T p 5435 d B s 0 S 0 M 0 Phase 4 for D 13 Enter to start Ends with Phase 4 for D2 15 Enter to start 10 Fil 2 Student Phase 4 for _ 17 Enter t
263. o start 7 tid 6 Committed 2 7 Ends with 1 t s n ont inue connection 12 Coordinator 127 0 0 1 5435 Files _ Role D2 User e Z 1 5434 13 NotStarted 127 0 0 1 12 Protocol byte RemoteBegin A 34 13 NotStarted Enter onnection 14 Coordinator 127 0 0 1 5435 Files _ Password password Role 14 Protocol byte RemoteBegin Conn io Coo r 0 0 1 5 es _ Role 14 Protocol byte IndexLookup P 14 Protocol byte IndexNext P 14 Protocol byte IndexNext c oordinate Connection 16 Coordinator 127 0 0 1 5435 Files D Role User guest connecting _ 127 0 0 1 5435 14 127 0 0 1 5435 4 Protocol About to Begin _ 127 0 0 1 5435 14 Enter to Continue 4 Protocol connecting D2 13 127 0 0 1 5435 14 Protocol byte IndexLookup t 14 Protocol byte IndexNext P col byte Data 14 Protocol byte IndexNext 3 P byte C eReader About to Begin D2 13 Enter to Continue 2 for tid 7 16 Protocol byte RemoteBegin 16 Protocol byte CloseConnection 16 Ends with 9 for D2 14 Enter for D 18 ter to start for D2 14 Enter tart En t art H DATA gt A x osp _ D osp Bilis x Home Share View t H DATA E gt B D2 osp L osp And table E on B Command Prompt OSP T p 5434 d A s 0 S 0 M 0 E Command Prompt OSP T p 5435 d B s 0 S 0 M 0 7 Ends with 1 Connection 12 Coordinator 127 0 0 1 5435 Files _ Role D2 User e me 12 Protocol byte RemoteBe
264. oDB service but the PyrrhoCmd client does not have the verbs such as find remove etc For simplicity we will allow PyrrhoCmd to be used by extending SQL a bit Let s allow SQL syntax that supports documents beginning with DOCUMENT as a standard type create table people doc document We won t specify primary key doc _id as this is the default Taking the example from page 7 insert into people values NAME sue AGE 26 STATUS A GROUPS news sports That is we allow Json literals in value lists Any document can be added to this people table Alas Mongo is case sensitive so we need capitals here or else we need double quotes below For the query example that follows on page 7 let s allow almost standard SQL select doc from people where doc age gt 18 order by doc age where we allow the standard dot notation in SQL to take us into the fields of documents We will of course support MongoDB s large collection of special operators and constructs With these we can rewrite the above query in an alternative form select from people where doc age Sgt 18 order by doc age From this we can begin to see how complex search conditions can be pushed down to remote partitions We can even allow MongoDB s explicit pipelines select aggregate people pipeline Smatch age Sgt 18 Sgroup _id Sage count Ssum 1 Ssort age 1 from static In such expressions Mongo uses
265. oes guarantee serialisability If the correctness of reads is not an issue they should be taken out of the transaction e g handled in a parallel connection If a transaction dos require correct reads and SSI is the best available in a DBMS true serialisability can be gained by upgrading reads to updates of the form set x x If the DBMS supports row versioning the application can check these at commit time But it seems wrong to leave transaction safety to the client 5 4 Transaction masters The enforcement of full ACID requires that for each resource there should be a single transaction master that enforces serialisability of transactions that access its data and any process that needs to know an up to date value in the resource or commit a change to this value needs to be able to communicate with that transaction master 46 The Pyrrho Book May 2015 Many designers of large systems dislike the notion of a single server playing such an important role There are two objections a it acts as a bottleneck at times of heavy traffic b it represents a single point of failure If the network is partitioned so that the transaction master is unreachable then no updates should occur If the transaction master is permanently out of action then the remaining network can elect a new one but it is not reasonable for two disconnected parts of the network to continue separately Partitioning a database horizontally for example on a
266. of standard SQL that should never be allowed for example ineffective REVOKE ON DROP NO ACTION branch transactions 7 The Pyrrho Book May 2015 expect all readers will have attended at least one course on Databases but the subject area is quite complex Actual building of database applications has been a neglected area in most university programmes The first set of practical exercises in Appendix 1 helps to motivate the discussion by showing some simple approaches to database application development 1 1 Download Pyrrho All editions of Pyrrho are available from www pyrrhodb org for immediate download Provided the NET framework has been installed it is possible to extract all of the files in the distribution to a single folder and start to use Pyrrho in this folder without making any system or registry changes The distribution contains a user manual called Pyrrho docx there is some overlap of material between Pyrrho docx and this book but the focus in this book is on general principles of databases while the manual contains more technical details about Pyrrho There are several editions of Pyrrho Professional and Open Source and the embedded versions of each They use the same relational engine API ACID transactions integrated security and multi user access but have a different database format pfl osp for security reasons There are corresponding client libraries PyrrhoLink dll OSPLink dll and embedded editio
267. ole name selected as the session role If this field is not specified the session role will be the default database role if the user is the database owner or has been granted this role it has the same name as the database or else the guest role which can access only PUBLIC objects Stop If a value is specified this means that Pyrrho is to load the database as it was at some past time User This field is supplied by infrastructure A CompoundConnectionString format is available for complicated multi file connections CompoundConnectionString ConnectionString ConnectionString ConnectionString Y If cs1 and cs2 are ConnectionStrings as specified above then cs1 cs2 is permitted For example A Files B Modify true C For this purpose the 3 separator sequences Hare assumed not to occur anywhere in the individual connection strings in particular they must not themselves be 211 The Pyrrho Book May 2015 compound The User field is supplied by infrastructure for the first of these connection strings but applies to all 212 The Pyrrho Book May 2015 Index to Syntax AbsoluteValue 194 Action 187 AddPeriodColumnList 184 Alias 190 Alter 182 AlterBody 183 AlterCheck 183 AlterColumn 183 AlterDomain 183 AlterMember 184 AlterOp 183 AlterTable 183 AlterType 184 AlterView 184 Any 193 Assignment 196 AttributeSpec 198 Authority 211 Avg 194
268. ommand Prompt PyrrhoCmd p 5436 _ P gt PyrrhoCmd Name osp D osp lt 2 items B lt DATA E B Name Date modified Osp 23 03 D osp 23 03 20 2 items DATA E C Name Osp We see the new configuration database in folder C C now initialises this empty database by creating the three tables _Database _Client and _Partition In C s server window press Enter five times 144 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 5 0 M EN Command Prompt OSP T d B p 5435 s E Command Prompt OSP T d C p 5436 s 0 S 0 PENGET RE xa JE OSP gt OSP T d B p 5435 s 0 5 0 Pyrrho DBMS c 2015 Malcolm Crowe and Uni A 0 0 Enter to star T d B p 5435 s 0 S Enter 15 9 19 March 2015 www pyrrhodb com Pyrrho DBMS c 2015 Malcolm Crowe and UniverPyrrho DBMS c 2015 Malcolm Crowe and PyrrhoDBMS protocol on 127 0 0 4 5 2 19 March 2015 www pyrrhodb com 5 2 19 March 2015 www pyrrhodb com Database folder PyrrhoDBMS protocol on 127 0 0 1 5434 Connecting D 3 127 0 0 1 5434 A Users atabase folder A About to Begin D 3 Enter to Continue 4 protocol byte ExecuteReader Connection 2 Coordinator 127 0 0 1 5435 FilesClosed D 3 Enter to Continue 2 Protocol byte RemoteBegin PyrrhoDBMS protocol on 127 0 0 1 5435 3 Coordinating Commit for tid 2 2 Protocol byte CloseConnection Database folder B Reco
269. on stoped the 3 servers emptied all 3 folders have started the servers again with the T flag 127 The Pyrrho Book May 2015 p 5436 s 0 S 0 M 0 5 0 M 0 tart up 2015 Malc c rsity of the W 5 ww pyrrhodb Database folde EN Command Prompt Mons She ew e t E DATA E A Name This folder is empty lt O items Be E t E DATA E B Name Date modified This folder is empty lt 0 items Bc F e to H DATA E gt C Name This folder is empty When we start to create the database D on the server A we get a message from server A acknowledging the connection 1 to the database D 128 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d E E OSP gt OSP T lt 3 35 fol 1 Files D User as Student Command Prompt PyrrhoCmd PyrrhoCmd p 5434 D Home Share View E t H DATA E gt A A Name This folder is empty In this mode you need to confirm each step of each transaction with the Enter key so for example in the next step create table E we get this EN Command Prompt osp T p 5434 d A s 0 S 0 EN Command Prompt OSP T d B p 5435 s 0 gt T 54 d A S M 0 JE P gt OSP T B p S 0 Student sp len 5 Home Share View 17 3 t E DATA E gt A Name _ D osp We see that PyrrhoCmd used Execut
270. on logs can be maintained they are often discarded after a time It is better practice to retain the logs or to adopt a DBMS design such as Pyrrho s where the transaction log is inseparable from the database On the other hand the user of DBMS based security makes a database much less portable It is no longer a simple matter of copying the database tables to another machine or domain since the authorisation identifiers will be different For example if a student develops a database at home there is an extra step required to ensure that the database is usable in the workplace environment namely to grant all privileges on the base tables to the student s user identity in the workplace grant all privileges on players to DOMAIN user or to PUBLIC of course 6 2 Forensic investigation of a database Pyrrho supports two kinds of investigation of a database First full log tables are maintained These are accessible to the current owner of the database or to an investigator specified in the server configuration file The log files allow tracing back to discover the full history of any object when it was created what changes to it were made and when it was dropped In each case full transaction details are recorded user role and timestamp Since objects can be renamed logs use numeric identifiers to refer to objects in the database Full details of the log tables are given in chapter 8 Using these tables it is always possible to obt
271. on of the tutorial is for OSP v5 2 27 March 2015 on Windows On this system my userid is Student with password password and Pyrrho has been installed in OSP where the student user has full control To replace the installed version of Pyrrho on this system with the latest version copy the Pyrrho distribution at http pyrrhodb com OSP52 zip into C Make sure there is no existing folder called OSP delete it if there is Then right click on OSP52 zip and select Extract here A5 1 Start up the servers For this exercise we will use 2 servers both on the local machine 127 0 0 1 but in separate database folders So have created empty folders A and B i e directly on the root of the drive not in OSP To keep security aspects simple everything is owned by student and student s password is password On my system everything is in E instead of C Command Prompt EN Command Prompt EN Command Prompt pie Shaws ie t E DATA E A Name lt O items EL Bl lsB t E DATA E gt B Name Date modified For the 2 servers we will use 2 command prompt windows On the first we issue the following commands 159 The Pyrrho Book May 2015 cd OSP OSP p 5434 d A s 0 S 0 M 0 The s S and M flags prevent the server starting the http https and Mongo services as we would need to allocate non conflicting ports for these The arguments are echoe
272. onn gt ConnectionString connectionString Srdr Sconn gt Execute SQLstring Srow Srdr gt Read Read returns 1 at the end of data so we continue while Srow is not an int while lis_int Srow Srow 0 etc for access to data returned Srdr gt Close 2 6 A first benchmark The C benchmark from the Transaction Processing Council Raab et al 2001 is a legendary test of database performance and models a clerical order entry OLTP system In this benchmark TPCC each new order transaction involves over 20 round trips to the database as the information is built up and submitted and transactional processing is required On supercomputing clusters transaction rates of 30 million per minute are reported Thomson et al 2012 report on the different approaches to achieving such high transaction rates other than using expensive hardware these all sacrifice something important from the above principles 18 The Pyrrho Book May 2015 Results for ACID RDMBS in PCs are more modest with 1500 2000 per minute being more normal In the past have benchmarked Pyrrho at 2000 per minute on a Dell laptop with Setup New Order Order Status Payment StockLevel Delivery Delivery Report Windows 7 On my current 8 core laptop ere and Windows 8 get just over 1000 per pc a ceait BE i ka n ana m m Order Number 6723 Number of Lines 13 W_tax D_tax 1123 minute but the CPU usage is only 14 as x a Supp_W Item Id I
273. ons Name BaseClass Description BTree lt K V gt ATree lt K V gt The main implementation of B Trees for a one level key that is IComparable CTree lt K V gt ATree lt K V gt A similar class where the key is a TypedValue SqlTree CTree lt TypedValue For one level indexes where the keys and values have TypedValue gt readonly strong types MTree CTree lt TRow long gt For multilevel indexes where the value type is Nullable lt long gt RTree CTree lt TRow TRow gt For multilevel indexes where the value type is a TRow Multisets are used for the final level in an RTree and so the RTree is not shareable Integer All integer data stored in the database uses a base 256 multiple precision format as follows The first byte contains the number of bytes following bytes n say data0 data1 data n 1 data0 is the most significant byte and the last byte the least significant The high order bit 0x80 in data0 is a sign bit if it is set the data including the sign bit is a 256s complement negative number that is if all the bits are taken together from most significant to least significant that data is an ordinary 2s complement binary number The maximum Integer value with this format is therefore 72039_4 35 The Pyrrho Book May 2015 Some special values Zero is represented as a single byte 0x00 giving the length as 0 1 is represented in two bytes 0x0
274. onsole WriteLine ex Message click Load In the code window j place the following code inside E private void Forml_Load object sender EventArgs e the Form1_Load method ad new MySqlDataAdapter select from member conn rds DataSet ad new MySqlDataAdapter select a f dataGridViewl DataSource ds Tables 0 rom member conn var ds new DataSet ad Fill ds dataGridView1 DataSource ds Tables 0 4 Try out the program you will see the data in the Members table though you may want to fix the sizes of the data grid and window and try again You will be able to change the data on screen but in order to update the database you need a second event handler 5 Close the program and go back to the design view Click the datagridview and find the RowValidated event in the Properties window Double click it and add the following code in the handler var dt dataGridView1 DataSource as DataTable private void dataGridViewl_RowValidated object sender DataGridViewCellEventArgs e i var ch dt GetChanges var dt dataGridViewl DataSource as DataTable if ch null var ch dt GetChanges if ch null t E var cb new MySqlCommandBuilder ad var cb new MySqlCommandBuilder ad ad UpdateCommand cb GetUpdateCommand ad Update ch ad UpdateCommand dt AcceptChanges cb GetUpdateCommand ad Update ch dt AcceptChanges 6 Let s demonstrate some other
275. ontent may be associated with multiple URIs by different people or to highlight different aspects of the content For example a web site that hosts a URI might also host a starting set of related URIs which in turn can be associated with it through other URIs Using these two observations we can see how semantic relationships can lead to knowledge discovery in the parts of the web where such associations have been recorded However only a small proportion of the World Wide Web uses these semantic notations Try http www cambridgesemantics com en_GB semantic university semantic web design patterns The closest analogue to such semantic associations in DBMS comes from the notion of data type as the next few sections indicate 8 1 URIs first steps A URI may look like a URL so that many URIs are constructed for uniqueness by starting with an organisation s domain name However the disadvantage of having a widely used URI is that the domain name may be accessed rather often and a way to avoid your web server being overloaded is to use a domain name for uniqueness but change the protocols part to something other than http e g urn The term IRI is also used for an international URI IRIs allow a wider character set but the distinction between URI and IRI is gradually being lost now that all UNICODE characters are allowed in URLs A common notation to indicate a URI is to enclose it in pointy brackets e g lt http abc com a un
276. orage along with a descriptor of the transaction itself Whether such ongoing transactions conflict can be determined by examining just these Physicals For example two updates to the same row of a table will conflict an insert in a table will conflict with dropping the table etc This means that transaction serialisation can be determined at the Physical Records level of the database There are two subtleties to the resulting design which apply equally to local and remote storage The first relates to relocation of Physicals the second to transaction conflicts where reads conflict with changes The relocation issue arises because Pyrrho uses the immutable defining addresses of data in Physical records so that for example a Column will refer to its parent Table by giving its defining address rather than its mutable name For this reason a group of Physicals in a transaction are very likely to refer to each other using their positions in the data file While transactions are in progress nobody can tell which transaction will commit first so the positions of Physicals in the data file are generally not known until the Commit succeeds The physical layer of the DBMS therefore relocates the transaction to its final place in the data file The read conflict issue is rather pedantic Pyrrho uses a very strict concept of transaction isolation and notes all data that a transaction reads If any of this data changes before the transaction commits
277. ot The given key is not found in the referenced table Column not found Multiset operand required not Object name expected for GRANT got Unexpected object type for GRANT Role revoke has ADMIN option not GRANT Privilege revoke has GRANT option not ADMIN Unsupported CREATE Domain not found in database Unknown privilege Domain or type must be specified for base column Cannot specify collate if domain name given NO ACTION is not supported Colon expected Unknown Alter type Unknown SET operation Table expected Illegal aggregation operation WHEN expected Ambiguous table or column reference Invalid POSITION Method not found in type Type not found FOR phrase is required Object not found Ambiguous field selector Field selector on non structured type The Pyrrho Book May 2015 42138 42139 42140 42141 42142 42143 42144 42145 42146 42147 42148 42149 42150 42151 42152 42153 42154 42155 42156 42157 42158 42159 42160 42161 42162 42163 42164 42165 42166 42167 44000 44001 44002 44003 44004 44005 203 Field selector not defined for on non type requires a static method requires an instance method NEW requires a user defined type constructor specified more than once Method selector on non structured type Cannot supply value for generated column OLD specified on insert trigger or NEW specified on delete trigger Cannot have two pr
278. ot try to imitate a locking model All good database architectures today support the ACID properties of transactions atomicity consistency isolation and durability Database products that use pessimistic locking such as SQL Server or Oracle acquire these locks on behalf of transactions by default and it is not usually necessary for an application to deal with these issues directly In a pessimistic locking product transactions can be delayed blocked while waiting for the required locks to become available A transaction can fail because it conflicts with another transaction For example with pessimistic locking the server may detect that two or more transactions have become deadlocked that is all of the transactions in the group is waiting for a lock that is held by another transaction in the group In these circumstances the server will abort one of the transactions and reclaim its locks so that other transactions in the group can proceed With pessimistic locking if a transaction reaches its commit point the commit will generally succeed If it does not complete it retains locks on database resources until it is rolled back With SQL Server for example once a transaction T begins it acquires locks on data that it accesses If it updates any data it acquires an exclusive lock on the data Until T commits or is rolled back no other transaction can access any data written by T or make any change to data read by T With optimis
279. ownership of the database to the grantee who must be a user not a role GranteeList PUBLIC Grantee Grantee Grantee USER id ROLE id See section 5 5 for the use of roles in Pyrrho Routine PROCEDURE id Type Type FUNCTION id Type Type YY MethodType METHOD id Type Type FOR id TRIGGER id A6 4 Type Type StandardType DefinedType Domain_id Type_id UriType StandardType BOOLEAN CharacterType FloatType IntegerType LobType NumericType DateTimeType IntervalType XML PASSWORD DOCUMENT DOCARRAY OBJECT The last four types are Pyrrho specific Password values show as Document is as in http bsonspec org DocArray is for the array variant used in Bson and Object is Objectld as in MongoDB Documents and Objectids are transmitted to clients as subtypes of byte data using Bson and byte 12 format respectively All four types have automatic conversion from strings Json to Bson for Document and DocArray while Objectld strings can be of hex digits or have four integer fields separated by colons time machine process count A top level document without an _id will be given an _id similar to MongoDB for the local machine Documents are considered equal if corresponding fields match CharacterType NATIONAL CHARACTER CHAR NCHAR VARCHAR VARYING int CHARACTER
280. password 127 0 0 1 5435 DATA E A password Continue studen During Phase 1 validation for the D participant we find we are not changing D so D can be closed Press Enter on B twice Command Prompt osp T p 5434 d 0 M EN Command Prompt OSP T d B p 5435 sl RW Command Prompt OSP T d C p 5436 s 0 E OSP gt osp T p 5434 d A s S 0 M 0 Connection 2 Coordinato 7 0 0 1 543 T 5434 d A s 0 O M 0 Enter to starConnecting D 5 127 0 0 1 5434 Pyrrho DBMS c 2015 Malcolm Crowe and UniverAbout to Begin D 5 Enter to Continue 5 2 19 March 2015 www pyrrhodb com 2 Protocol byte RemoteBegin PyrrhoDBMS protocol on 127 1 5434 2 Protocol byte Fetch DbStorage Flush complete for C osp len 979 atabase folder A 2 Protocol byte Fetch Phase 4 for _ 4 Enter to start Connection 2 Coordinator 127 0 0 1 5435 FilesConnection 4 Coordinato 27 0 0 1 543 3 tid 2 Committed 2 Protocol byte RemoteBegin Protocol byte RemoteBegin Connecting D 5 127 0 0 1 5435 2 Protocol byte CloseConnection Protocol byte IndexLookup About to Begin D 5 Enter to Continue Exception 00000 Protocol byte IndexNext Connecting _ 127 0 0 1 5435 6 127 0 0 1 5435 Phase 1 5 for _ 4 Enter to start Phase 2 for _ 4 Enter to start Phase 3 for _ 4 Enter to start StartCommit for _ osp at 34 2 Rollback Protocol byte IndexLookup About to Begin _ 127 0 0 1 5435 6 Enter to Continue 2 Ends wit
281. pendency below As of v 5 0 we will use the following schema for _ _Client Server Client User Password We locally store entries for which Server us This table is maintained automatically don t update it Passwords use Pyrrho s password type so are not readable The user and password information enables access to the configuration database on the client _Database Name Server Password ServerRole Remote RemoteUser RemotePassword Remote Server references _Client We locally store entries for which Server us Passwords use Pyrrho s password type so are not readable but they must be supplied when this table is updated to enable server server communication The remoteuser and remotepassword information enable server server access to the named database on the remote server The password information enables access to the configuration database on the server _Partition Base BaseServer BasePassword Table PartitionName PartitionServer PartitionServerConfigUser PartitionServerConfigPassword SegmentName Column MinValue MaxValue IncludeMin IncludeMax Table and Column are positions in the base database we understand that the partition database has appropriate entries in its schema and a mapping from the base positions We locally store entries where BaseServer us If you create such an entry Pyrrho automatically defines the table in the partition database and makes a Partition1 record in the partition datab
282. pitals Se we end up with URL s like http localhost 8180 mydb mydb MYTABLE 6 You can view the metadata such as PIE HISTOGRAM etc for database objects such as tables views procedures and table columns by using the RoleSObject sytem table on the command line you would say table RoleSObject For columns of views or stored functions there is another system table called RoleSSubobject which does not seem to be in the manual just now You should be able to modify metadata for objects and subobjects by using the keywords ADD and DROP you don t really need ADD as it is the default behaviour e g alter table mytable drop histogram alter view myview alter someviewcolumn drop x alter function myfunc int alter someresultcolumn y etc 7 There are ways of supplying style sheets hidden in the Description metadata string The manual s notes on Metadata read sec 7 2 Metadata ATTRIBUTE CAPTION ENTITY HISTOGRAM LEGEND LINE POINTS PIE X Y CAPPED USEPOWEROF2SIZES BACKGROUND DROPDUPS SPARSE MAX int SIZE int string iri The Metadata flags and the string constraint are Pyrrho extensions Attribute and Entity affect XML output in the role Caption Histogram Legend Line Points Pie X and Y affect HTML output in the role Other metadata keywords are for MongoDB The string is for a description but if it begins with a lt it will be included
283. porary files If all is well these temporary files do not need to be read and can be removed once all participants have acknowledged the commit request Transaction conflicts This section examines the verification step that occurs during the first stage of Commit For each physical record P that has been added to the database file since the start of the local transaction T we e check for conflict between P and T conflict occurs if P alters or drops some data that T has accessed or otherwise makes T impossible to commit e install P in T Let D be the state of the database at the start of T At the conclusion of Commit1 T has installed all of the P records following its own physical records P T DP P But if T now commits its physical records P will follow all the P records in the database file The database resulting from Commit3 will have all P installed after all P ie D DPP Part of the job of the verification step in Commit1 is to ensure that these two states are equivalent see section 4 2 2 Note that both P and P are sequences of physical records P pop1 pn etc The verification step performed by Pyrrho goes one stage beyond this requirement by considering what data T took into account in proposing its changes P We do this by considering instead the set P of operations that are read constraints C or proposed physicals P of T We now require that DP P DPP The entries in C are called ReadConstraints this is a
284. posed in the local transaction are relocated onto the end of the database Thus the defining positions of any new data will be different from those created in memory for the local transaction the entire local transaction structure is therefore forgotten even in the case of a successful commit Instead the database is updated by reading the new records back from the disk or disk cache Thus all changes are applied twice once in the local transaction and then after transaction commit but the first can be usefully seen as a validation step and involves many operations that do not need to be repeated at the commit stage evaluation of expressions check constraints execution of stored procedures etc These approaches to the design have some strange effects For example any data structures that are not transaction specific must avoid maintaining pointers to the logical level structures such as Table TableColumn since these may no longer be current for the next transaction The current versions must be obtained afresh from the Database data structure either by name or by defining position as appropriate Because of transaction separation checking for transaction conflicts cannot be done at the level of the logical database Level 3 It is done at the physical level Level 2 with the help of a set of rules for what constitutes a conflict Data relating to read constraints needs to be passed down to level 2 in a special data structure since t
285. pt and in practice such documents are seen as redundant duplication and deleted as a matter of routine As a result for real durability database designers need to create special tables journals histories etc when such records are a legal requirement In the Pyrrho DBMS the transaction log is precisely the durable record of the database and so it cannot be deleted without deleting the entire database The current state of the data with its indexes etc is in memory A similar approach has been reported for in memory column oriented DBMS by Wust et al 2012 This architecture brings significant advantages not only do we have durability of the transaction record but two other advantages a committing a transaction involves appending the transaction record to the end of the file and b the amount of writing to the disk during operation is reduced according to benchmark measurements for Pyrrho Crowe 2005 by a factor of 70 This large difference in performance arises because in the traditional database architecture it is not only the current state of the data that is held on disk but also all of the indexes and other data structures and so any change to the database results in changes to many parts of the disk files In 2004 when Pyrrho s design was first published objections from the database community centred on the large amount of memory that would be needed for real commercial databases In practice databases of 20GB are regarded
286. pter applies within the connection s thread collecting the database from the server s level 3 base thread at the start of each transaction and synchronising with it when the transaction commits In the next chapter we will consider the effects of this approach to transactions and compare with the practice in other DBMS The disadvantage of the design is that a cold restart of the database server requires re reading the entire transaction log some countervailing measures are 1 using a multi database design since Pyrrho supports multi database connections 2 the technique of partition sequencing discussed in chapter 10 Key features of Pyrrho s design In Chapter 9 we will consider an approach to distributed databases where a server can play any or all of three roles in relation to a particular database storage transaction serialisation and query processing Storage is basically the transaction log or a copy the physical database or PhysBase transaction serialisation is when a set of proposed changes are appended to the master copy of the transaction log and for query processing the server needs to have the indexes and database objects implemented in the logical Database class During a transaction the database connection is to a set of LocalTransactions or proxies that are based on Database snapshots Each has access to the physical layer for fetching data from base tables using a subclass of the PhysBase for example th
287. r sections 3 1 Constraints It should be possible to apply a domain constraint e g to specify that a number should be in a certain range or have a default value It should be possible in addition to specify a constraint for a column or an automatic rule to generate the value of a column based on other attributes Several popular ways of getting the database to generate a primary key for a new row are available It should be possible to specify a constraint for a table for example that all values of a particular column are found in the table The SQL standard imposes many restrictions on the expressions used to define such constraints and these are enforced to a greater or lesser degree by different databases Pyrrho allows any search condition to be used as a column or table constraint and allows such constraints to be modified later However it prevents adding a constraint that is not currently satisfied by data in the table and does not allow any operation not even a step in a transaction that violates any constraint Example 1 database The PyrhoSvr should already be running Pyrrho DBMS lt c gt 2612 Malcolm Crowe and University of the West of Scotland 4 8 18 February 2013 www pyrrhodb com NOT Minimising Disk Reads PyrrhoDBMS protocol on 127 6 6 1 5433 HTTP service started on port 8180 HTTPS service started on port 8133 Start up a command window using the command 24 The Pyrrho Book May 2015 Pyrrhocmd Bank
288. r transaction See sec 5 2 3 void Close Close the channel to the database engine string ConnectionString Get the connection string for the connection PyrrhoCommand Create an object for carrying out an Sql command as in CreateCommand IDbCommand void Delete object ob Delete the row corresponding to this object void Get object ob string rurl The rurl should be a partial REST url the portion following the Role component and ob should be a new instance of the target class object Get string rurl The rurl should be a partial REST url the portion following the Role component that targets a class in the client application string GetFileNames Returns the names of accessible databases void Open Open the channel to the database engine void Post object ob The object should be a new row for a base table 208 The Pyrrho Book May 2015 void Put object old object The first object should hold the content of a bast table row ob that was obtained from the database The second object should be an updated version Create a new PyrrhoConnect with the given connection string Documentation about the connection string is in section 6 4 Repositions the IDataReader to just before the start of the data void SetRole string s Set the role for the connection PyrrhoConnect string cs void ResetReader The Get Put Post and Delete methods assume that the classes corresponding to the releva
289. r Property Explanation int years The years part of the time interval int months The months part of the time interval long ticks The ticks part of the time interval static long TicksPerSecond Gets the constant number of ticks per second static string ToString Formats the above data as e g Oyr 3mo 567493820000ti A9 9 PyrrhoReader This class is Pyrrho s implementation of IDataReader The only additional members of PyrrhoReader are from version 4 4 Method or Property Explanation string DataSubtypeName int Returns the domain or type name of the actual type of the ith i column in the current row Usually this will be the same as DataTypeName 209 The Pyrrho Book May 2015 string Description int i Returns the description metadata of the ith column T GetEntity lt T gt Used in strongly typed PyrrhoReaders as in ExecuteTable lt T gt string Output int i Returns the output flag of the ith column string Url int i Returns the web metadata url of the ith column A9 10 PyrrhoRow PyrrhoRow is used only when required for values of structured types The methods and properties of PyrrhoRow are Method or Property Explanation List lt PyrrhoColumn gt columns The names of the fields of the row object data The values of the fields may be null This is the indexer for PyrrhoRow indexed by column number or column name string subTypes The names of the actual types for the current row
290. r communication server roles and partitions When changes are committed affected databases are unloaded and a background process is started to reload them Pyrrho does try to notify affected servers using the same mechanism as for any update to a distributed database this will be an area for continuing improvements Note however that the server passwords in the configuration tables are for enabling access from one server to another using standard operating system security for the accounts under which the servers have been configured to run The partition base credentials enable access to the base database of the partition being configured On a single server or in a single domain it is quite likely that a single account and password will be used in all or most of the tables As a special case the entry in the _Database table for a partition will have all 3 server roles and the remote information will be for the base server 9 3 Auto partition algorithm for _ Maintain a list D of servers mentioned in our part of the _ database This list is called directServers in the code Maintain a list L of all servers mentioned in the distributed _ database This list is initially constructed as follows Add us to L then for each server in L add its D list and containue until the list stops growing L is marked for resfresh after an update to _ If any servers are offline a background process retries the refresh L every 20 seconds Then to
291. r defined type Ordering functions can simply specify equality or allow lt and gt comparison FULL The ordering function can specify a relative ordering in which case the corresponding routine takes two parameters of the udt and returns 1 O or 1 A mapping ordering function defines a numeric value for each value of the udt which can then be compared The other option you can specify STATE merely tests for componentwise equality 8 8 Stored Procedures and Methods In SQL2011 the syntax v is not supported for variable references and instead variables are identified by qualified identifier chains of form a b v The syntax for parameters is not supported either In SQL2011 2 11 50 we see that procedures never have a returns clause functions should be used if a value is to be returned and procedure parameters can be declared IN OUT or INOUT and can be RESULT parameters Variables can be ROW types and collection types For functions TABLE is a valid RETURNS type it is strictly speaking a multiset in SQL2011 terminology From SQL2011 2 6 39 we see that RETURN TABLE queryexpression is a valid return statement Here are some outlines of procedure statements specified in SQL2011 4 and supported in Pyrrho Complete syntax summaries for Pyrrho are given in Appendix 6 The operation of the security model for routines is rather subtle All routines operate with definer s rights by default but access to them is controlled accord
292. real time on the physical database On Windows systems the user identity is obtained from Windows and the default role has the same name as the database The user can specify another role in the connection string or specified by the SET ROLE statement provided this role has been assigned to them Pyrrho allows database objects to be renamed or altered by holders of the appropriate permissions but such renaming and alteration applies to the current role so that a database object can have different names in different roles By default all roles in a Pyrrho database have a default data model based on the base tables their columns and using foreign keys as navigable properties Composite keys use the list notation for values e g 3 4 and the name is the reserved word key which can be suffixed by the property name of the key component The default data model can be modified on a per role basis to provide more user friendly entity and column names and user friendly descriptions of these entities and properties Tables and columns can be flagged as entities and attributes as desired For example roles could be defined for users in different countries using entity names property names and descriptions appropriate to the language of the country giving access to localised columns or views The localisation of columns is facilitated by the Pyrrho specific UPDATE clause for generated columns which can perform lookups or casts behind the scenes These
293. rency control and minimises this sort of delay it also rigorously enforces transaction isolation so that it is impossible to know anything about any ongoing transaction The difficulties caused by the bad behaviour of pessimistic locking transaction management are far reaching and have even led to many businesses deciding that they cannot afford transaction management Other aspects of RDBMS technology have also been blamed for poor performance and there are many vendors offering no SQL databases or columnar databases Many commercial DBMS prohibit benchmark testing of their products in their licensing arrangements Pyrrho positively invites benchmarking Crowe 2005 and despite its rigour its performance is comparable with commercial products 2 5 Application programming interfaces ADO NET There are numerous APIs for contacting database servers the oldest in common use are ODBC and JDBC Java Persistence had a brief vogue as did Microsoft s LINQ The PHP API is like a cut down version of ADO NET and versions of ADO NET are also used for MySQL and Pyrrho We will use some ADO NET sample code in the lab The following sequence is typical of standard ADO NET The first step uses the database connection string Every database has its own style of connection string for lots of examples see www connectionstrings com var conn new XXXConnection connectionstring var cmd conn CreateCommand cmd CommandText some SQL SELEC
294. rho how to deal with values of the new domain The OWL namespace prefixes and standard types are predefined in Pyrrho Pyrrho does not use semantic reasoning so for example will not know of the relationship between kilowatts and watts or of watts and amps Pyrrho supports OWL literal syntax e g 2 37 watts or 2 37 units watt is a valid literal of the above domain Note the use of double quotes for such literals double quotes normally create identifiers but the syntax gives a literal The type following the can be a domain name as here or take the OWL forms units watt or lt http sweet jpl nasa gov 1 1 units owl watt gt Note that O is a special character in OWL string literals which Pyrrho interprets as introducing a collation However it is much more convenient to allow abbreviations for units so that 2 37 W would also be allowed The formal syntax for the representation part here is StandardType UriType where UriType is defined as Abbrev_id Prefix_id id uri A uri in this syntax is delimited with lt gt The namespace prefix must be one of the standard namespaces given above see XmlOption syntax have been previously defined in the database using the CREATE XMLNAMESPACES statement or declared in a preceding XmlOption The provision of an abbreviation is enough to specify a default parser for a new Domain The parser will use the underlying type and the supplied abbreviation and the abbreviation is allowed
295. rompt osp T p 5434 d A s 0 S 0 M 0 Command Prompt OSP T d B p 5435 s 0 S 0 M 0 Phase 4 for _ 7 Enter to start 7 tid 4 Committed 5 Protocol byte RemoteBegin IndexLookup IndexNext IndexLookup Se ee IndexNext ontinue Exception 00000 3 Rollback 5 Protocol byte Prepare Prepare 2 physicals Record out to Pref t to Chec Prepare complete 5 Protocol byte CheckSerialisation Bl lA x EX Command Prompt PyrrhoCmd p 5435 _ Press Enter again four more times Command Prompt osp T p 5434 d A s 0 S 0 EN Command Prompt OSP T d B p 5435 s 0 S 0 M 0 8 tid 5 Committed r ter to Continue 6 Protocol byte RemoteBegin 6 Protocol byte IndexLookup 6 Protocol byte IndexNext 6 Protocol byte IndexLookup 6 Protocol byte IndexNext 4 Protocol byte CloseConnection Exception 00000 4 Rollback 4 Ends with 9 6 Protocol byte Prepare Prepare 2 physicals 6 Protocol byte CheckSerialisation 6 Protocol byte CheckSerialisation Continue Home Share View E DATA E A 127 0 0 1 5435 4 a 7 0 0 1 5434 Student LJ osp _ D osp lt 2 items B a De x e t E DATA E gt B Name D osp L _ 127 0 0 1 5434 23 03 2015 15 What has happened here is that B locked the database and checked serialisation again finding all is fine it has written all of the tran
296. rotocol byte Prepare Phase 1 for _ 9 Enter to start Prepare 1 physicals About to Prepare _ 127 0 0 1 5435 6 Enter to Continue Record About to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Cor Prepare 0 rdCs Phase 1 5 for _ 9 Enter to start esPrepare complete AA About to CheckSerialisation _ 127 0 0 1 5435 6 Enter to Con 4 Protocol byte CheckSerialisation phase 1 5 for 5 Enter to start 4 Protocol byte CheckSerialisation phase 2 for 6 Enter to start 4 Protocol byte Request DbStorage Flush complete for C _ _ 127 0 0 1 5435 1137 _ 12 DbStorage Flush complete for B _ _ 124phase 2 for _ 9 Enter to start Connection 6 Coordinator 127 0 0 1 5434anout to Request _ 127 0 0 1 5435 6 Enter to Continue Connecting D 9 127 0 0 1 5434 Phase 3 for _ 5 Enter to start About to Begin D 9 Enter to Continue Connecting D 5 127 0 0 1 5435 About to Begin D 5 Enter to Continue Share View P Cmd p into _Database values D 127 0 0 1 5436 2 password 127 0 0 1 5435 stude lt DATA E A Name osp D osp Now B is synchronising D with A again On B press Enter and on C press Enter several times until the transaction is committed 149 The Pyrrho Book May 2015 EN Command Prompt osp T p 5434 d A s 0 S 0 M Command Prompt OSP T d B p 5435 s l i Command Prompt OSP T d C p 5436 s 0 S 0 M 0 FilesPrepare 0 rdCs Phase 2 for _ 5 Enter to start
297. rrhoCmd p 5436 D 151 The Pyrrho Book May 2015 E Command Prompt osp T p 5434 d A s 0 S 0 M ij Command Prompt OSP T d B p 5435 s l Command Prompt OSP T d C p 5436 s 0 S 0 M 0 eg 4 Protocol byte CheckSerialisation Phase 2 for 9 Enter to start 4 Protocol byte CheckSerialisation About to Request _ 127 0 0 1 5435 6 Enter to Continue 4 Protocol byte Request Phase 3 for _ 5 Enter to start DbStorage Flush complete for B _ _ 12 Connecting D 5 127 0 0 1 5435 Connection 6 Coordinator 127 0 0 1 5434anout to Begin D 5 Enter to Continue Connecting D 9 127 0 0 1 5434 StartCommit for _ osp at 974 About to Begin D 9 Enter to Continue DbStorage Flush complete for C _ osp len 1142 6 Protocol byte RemoteBegin Phase 3 for D 7 Enter to start 4 Protocol byte RemoteCommit Phase 3 for _ 9 Enter to start StartCommit for _ osp at 1137 About to Commit _ 127 0 0 1 5435 6 Enter to Continue PbStorage Flush complete for B _ oSP Icjosed _ 127 0 0 1 5435 6 Enter to Continue 4 Ends with 31 Phase 4 for _ 5 Enter to start 6 Protocol byte CloseConnection Phase 4 for D 7 Enter to start Exception 00000 Closed D 5 Enter to Continue 6 Rollback Phase 4 for _ 9 Enter to start About to Close D 9 Enter to Continue 1 tid 1 Committed Closed D 9 Enter to Continue 1 Ends with 1 6 Ends with 9 Connection 5 Files D User asusrog Student EX Command Prompt PyrrhoCmd p
298. rsorSpecification DECLARE HandlerType HANDLER FOR ConditionList Statement Declarations of identifiers cursors and handlers are specific to a scope in a SQL routine HandlerType CONTINUE EXIT UNDO ConditionList Condition Condition Condition ConditionCode SQLEXCEPTION SQLWARNING NOT FOUND The ConditionCode not_found is acceptable as an alternative to not found Signal SIGNAL ConditionCode SET Condinfo Value CondInfo Value RESIGNAL ConditionCode SET CondInfo Value CondInfo Value ConditionCode Condition_id SQLSTATE string Condinfo CLASS ORIGIN SUBCLASS _ORIGIN CONSTRAINT_CATALOG CONSTRAINT_SCHEMA CONSTRAINT_NAME CATALOG_NAME SCHEMA_NAME TABLE_NAME COLUMN_NAME CURSOR_NAME MESSAGE_TEXT GetDiagnostics GET DIAGNOSTICS Target ItemName Target ItemName ItemName NUMBER MORE COMMAND_FUNCTION COMMAND_FUNCTION_CODE DYNAMIC_FUNCTION DYNAMIC_FUNCTION_CODE ROW_COUNT TRANSACTIONS_ COMMITTED TRANSACTIONS ROLLED_BACK TRANSACTION_ACTIVE CATALOG_NAME CLASS_ORIGIN COLUMN_NAME CONDITION_ NUMBER CONNECTION_NAME CONSTRAINT_CATALOG CONSTRAINT_NAME CONSTRAINT_SCHEMA CURSOR_NAME MESSAGE_LENGTH MESSAGE_OCTET_LENGTH MESSAGE_TEXT PARAMETER_MODE PARAMETER_NAME PARAMETER_ORDINAL_POSITION RETURNED_SQLSTATE ROUTINE_CATALOG ROUTINE_NAME 197 The Pyrrho Book May 2015 ROUTINE_SCH
299. rst b b rs next catch Exception e System out println e getMessage 3 5 SWI Prolog The Open Source Edition of Pyrrho also comes with some support for SWI Prolog This is contained in a module pyrrho pl which is part of the distribution The code is at an early stage so comments are welcome The following documentation uses the conventions of the SWI Prolog project The interface with SWI Prolog is implemented by providing SWI Prolog support for the Pyrrho protocol see technical details in the Pyrrho manual The following publicly visible functions are currently supported connect Conn ConnectionString Establish a connection to the Open Source Pyrrho server Conn has the form conn InStream InBuffer OutStream OutBuffer Codes in OutBuffer are held in reverse order sql_reader Conn0 Conni SQLString Columns Like ExecuteReader on the connection Conn0 Conn1 is the updated connection Columns is a list of entries of form column Name Type read_row Conn0 Conn1 Columns Row Reads the next row fails if there is no next row from the connection Conn0 Conn1 is the updated connection Columns is the column list as returned from sql_reader Row is a list of corresponding values for the current row close_reader Conn Closes the reader on connection Conn field Columns Row Name Value Extracts a named value from a row The atom null is used for
300. ry iTables AUTHOR LIBRARIAN Delete References GrantDelete GrantReferenc les Library Domains INTEGER PUBLIC Usage GrantUsage PUBLIC i Domains INTEGER LIBRARIAN Usage PUBLIC i Domains CHAR PUBLIC iUsage GrantUsage PUBLIC i i Domains CHAR LIBRARIAN Usage PUBLIC i Columns AUTHOR ID Library iSelect Insert Update GrantSelect GrantInse GrantUpdate Library Columns AUTHOR ID itLIBRARIANiSelect Insert Update GrantSelect GrantInse rt GrantUpdate Library i Co lumns AUTHOR NAME Library iSelect Insert Update GrantSelect GrantInse rt GrantUpdate Library As can be seen in the illustration the fields in this system table are ObjectType Name Grantee Privilege and Owner Note the different privileges associated with database objects e g tables and columns 59 The Pyrrho Book May 2015 Chapter 7 Role based modelling and legacy data In the last chapter we examined roles and security The roles assigned to a user and the permissions assigned to the roles control what a user is able to do For the reasons outlined in the last chapter Pyrrho requires the user to exercise one role at a time In this chapter we explore a major advantage of this approach in that schema changes made by a user in Pyrrho are local to the role so that each role may have a different data model We will see that this allows data analytics to operate conveniently and in
301. s E competition on a single resource Note this experiment is not relevant with Pyrrho First restoring the original contents by client A EGIN TRANSACTION H E FROM Accounts ERT INTO Accounts acctID balance VALUES 101 1000 ERT INTO Accounts acctID balance VALUES 202 2000 CT FROM Accounts n HA oO Ww 2 hw uv dE T The Pyrrho Book May 2015 COMMIT client A starts SELECT acctID balance FROM Accounts WHERE acctID 101 client B starts SELECT acctID balance FROM Accounts WHERE acctID 101 client A continues UPDATE Accounts SET balance balance 200 WHERE acctID 101 client B continues UPDATE Accounts SET balance balance 500 WHERE acctID 101 the client which survived will commit SELECT acctID balance FROM Accounts WHERE acctID 101 COMMIT Experiment 5 Competition on two resources in different order First restoring the original contents by client A BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUES 101 1000 INSERT INTO Accounts acctID balance VALUES 202 2000 SELECT FROM Accounts COMMIT 1 Client A starts BEGIN TRANSACTION UPDATE Accounts SET balance balance 100 WHERE acctID 101 2
302. s either completed COMMIT or abandoned ROLLBACK All practical DBMS allow concurrent access so that several clients can be operating on the database at the same time Not all of them will be making changes to the database and in any case changes are likely to affect different parts of the database and so won t affect each other The theory of database transactions considers each transaction as a sequence of read and write operations each occurring at a particular time Concurrent transactions are transactions whose operations overlap in time they are valid as long as they are serialisable that is if the reads and writes could have achieved the same 16 The Pyrrho Book May 2015 results if all of the operations of the transactions had been moved in time so that the transactions do not overlap Many DBMS products write changes to disk storage before the transaction commits in times past this was needed since some transactions might involve too much data to be held in memory Researchers have examined higher level disk operations to improve this mechanism e g Ouyang et al 2011 Pyrrho s approach is to assume memory is large enough to avoid doing any writing to non volatile storage until the transaction commits In the database literature transactions are called ACID atomic consistent isolated and durable All DBMSs provide for transactions but most allow exceptions to the ACID principles Allowing exceptions means sacrificing cons
303. s m where current_user like S firstname We want all members of the club to be able to execute these procedures We could simply grant execute on these procedures to public However it is better practice to grant these permissions instead to a role say membergames and allow any member to use this role Create role membergames Matches between members for ranking purposes Grant execute on procedure claim int int to role membergames Grant execute on procedure agree int to role membergames Grant membergames to public This example could be extended by considering the actual use made of the Played table in calculating the current rankings etc 6 1 Application or DBMS based security In many commercial environments DBMS security is a neglected topic This is partially excusable if the only way to use a database is through a set of applications whose use is subject to strong authentication and authorisation mechanisms but it should be recognised that a good security structure in the databases can lead to greatly enhanced forensic opportunities These will be lost if the tables in a database are all public or worse if the tables all belong to the database administrator and the database administrator identity is used by all applications In many commercial DBMS it is very hard to discover who made a particular change to the database or when or what value was there before the change occurred Although transacti
304. s ownership and permissions Database partitioning is configured using a single table _ Partition inthe _ configuration database on the base database s server and operates transparently to SQL clients Thus some databases hosted on a server may be partitions a partitioned table contains non overlapping segments allocated to partitions while the rest of its data remains in the base database Partition definition is independent of the definition of constraints such as primary and foreign keys checks and triggers but obviously the database designer needs to consider whether their operation will result in cross partition traffic In particular traversing an indexed partitioned table will in general involve an n way merge and the checking of constraints that do not involve partitioning columns will result in broadcasts to all partitions This design allows dynamic reconfiguration of live databases Each partitioned table contains a number of segments defined by 1 or more ValueBounds structures for particular columns The columns used for partitioning should be indexed in the table Currently the _Partition table has the following form _Partition PartitionName PartitionServer PartitionServerConfigUser PartitionServerConfigPassword Base BaseServer Table SegmentName Column MinValue MaxValue IncludeMin IncludeMax The table is indexed by Base PartitionName Table SegmentName Column It includes the credentials needed to
305. s that transactions for that connection are serialised by the client application so that any thread specific data is disposed of at transaction boundaries Finally the granularity of locking can be adjusted For normal row based CRUD operations Pyrrho detects conflicts at the row level and detects conflicts at the level of database objects only when schema changes are being made This level of granularity is slightly harder to achieve in pessimistic systems since a great deal of work may be required in advance to identify exactly which rows will be updated 5 3 Snapshot isolation Snapshot isolation is when transactions cannot see the activities of concurrent transactions but proceeds with a view of how the database stood at the time the transaction started Many DBMSs support snapshot isolation SI as an optional mode Pyrrho enforces it In databases that provide so called serialisable snapshot isolation SSI there is a check made before a transaction commits that no updates since the snapshot conflict with any updates the transaction is 45 The Pyrrho Book May 2015 about to commit It used to be claimed that this results in serialisable transactions but it does not Transactions are only serialisable if all of their activities reads and writes have effect as if there is no concurrency i e there is an ordering of the effective times of transactions such that the same results are achieved The commit time of a transaction is w
306. s very important Assuming that the processing envisaged by the application involves zero or more transactions we can imagine that a transaction involves one or more TCP IP sessions We will discuss this further later in this course At this stage though we will note that if the server needs to preserve information about the whole series of transactions session state from one TCP IP session to the next this will require management on multi server installations where subsequent sessions might be on another server Either steps will be taken to ensure that subsequent requests from the same client are dealt with by the same server server affinity or servers will need to share session state somehow 40 The Pyrrho Book May 2015 Another issue is that the TCP IP setup time referred to earlier can become a significant cost Some client server systems create pools of connections and threads to try to make this process as efficient as possible For both of these reasons there is an argument for holding a connection open for the duration of a transaction even though this might be quite a long time 4 6 Database concurrency In the meantime the database server needs to be able to deal with other clients With this design it becomes inevitable that the database server will manage multiple clients concurrently dealing with requests in different threads Even requests from different clients for the same database may be handled at
307. saction details to disk in a specially named file This filename records the sizes of the transaction logs for the participating databases and the contents of the file contain binary details of the changes being made In this case the filename is __ _ 127 0 0 1 5434 974 _ 127 0 0 1 5435 974 0sp which merely shows that both configuration databases are still in their initialised state the file size of 979 bytes includes an end of file marker Press Enter again twice to make a Request to server A 138 The Pyrrho Book May 2015 Command Prompt osp T p 5434 d A s 0 S 0 E Command Prompt OSP T d B p 5435 s 0 S 0 M 0 1 Coordinating Commit for tid 1 Reconfigure y on _ 127 0 e 1 for _ 5 Enter to start 1 for D 7 Enter to start to Close D Enter to Continue _ 127 Enter to Continu eriali K 34 6 Enter ontinue Enter to tinue _ _ 127 0 0 1 5434 974 127 0 0 1 5435 974 osp len 105 4 6 Enter to Continue E DATA E A hoCmd p 5435 into _Datab va Gol het 5435 password 0 0 Student 127 0 0 1 543 _ _ 127 0 0 1 5434 A has now also recorded the transaction details with its own similarly named file If you look at this stage you will see that the two temporary transaction files have different sizes Still in B s window press Enter again to start phase 3 s 0 S 0 EN Command Prompt OSP T d
308. saction for database D The last line says that transaction 1 on connection 1 has been committed The connection is to the command processor and will end with the session as we will see later Similarly use the Enter key 5 times each for the next two steps insert into E values 1 One insert into E values 2 Two and 3 times for the read only transaction no need for phases 1 5 or 2 table E E Command Prompt OSP T p 5434 d A s 0 S 0 M 0 O Pr 1 f t Share View t H DATA E gt A A Name _ D osp Show the Logs file etc again if you want and close the session with AC 170 The Pyrrho Book May 2015 A5 8 Step 4 in detail PyrrhoCmd p 5434 _ insert into _Partition values D2 127 0 0 1 5435 Student password D 127 0 0 1 5434 password E E2 F 2 2 true true This time when you issue this command the first stage is to construct the configuration file on A Enter 5 times On the sixth Enter A begins the connection 1 to B and B creates the new partition D2 on B You can see that B s connection is coordinated by A and the role D for the new database D2 identifies it as a partition with base D EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EM Command Prompt OSP T p 5435 d B s 0 S 0 M 0 West of Scotland ge Flush complete fo t E DATA E gt A lt 2 items D2 osp 30 0
309. se 1 5 for D2 15 Enter to start A t to CheckSerialisation D2 13 Enter to Continue ase 2 for _ 12 Enter to start bStor lush complete for 127 0 1 5434 974 127 0 0 1 5435 Phase 2 for D 13 Enter to start D _ 127 0 1 5434 974 127 0 0 1 54357 1 Protocol b Phase 2 for D2 15 Enter to start com About to Request D2 13 E p 17 oe to pert h comple hoCmd gt create tabl rt into into Home Share View t E DATA E gt A osp _0127 0 0 1 5434 974 012 _ D osp D _ 127 0 0 1 5434 974 _ 127 0 0 1 54 Student password D 127 0 0 1 4 items B 3 D2 _ 127 0 0 1 543 30 03 2015 22 43 D2 osp _ _0127 0 0 1 5434 L osp A few more Enters and A now send the Commit for the D2 transaction on B B commits and removes the Saved data 175 The Pyrrho Book May 2015 EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 out to CheckSerialisation D2 13 Enter to Continue EN Command Prompt OSP T p 5435 d B s 0 S 0 M 0 erialisation Phase 2 for D 13 Enter to start Storage Flush complete for A D _ 127 0 0 1 5434 974 ase 2 for D2 15 Enter to start out to Request D2 13 Enter to Continue About to Request _ 127 0 O 1 5435 14 Enter to Continue ase 3 for _ 12 Enter to start p at 974 mplete for B _ _ 12 B D2 _ 127 0 1 54 974 127 0 0 1 543 7 0 0 1 5434 974 _0127 0 0 1 5435 F1 p r osp len 350
310. se Languages SQL Part 4 Persistent Stored Modules ISO IEC 9075 14 2008 Information technology Database languages SQL Part 14 XML Related Specifications SQL XML International Standards Organisation 2011 SWI Prolog www swi prolog org Thomson A Diamond T Weng S C Ren K Shao P amp Abadi D J 2012 May Calvin fast distributed transactions for partitioned database systems In Proceedings of the 2012 ACM SIGMOD International Conference on Management of Data pp 1 12 ACM Tozun P Porobic D Branco M 2012 Transaction Processing http dias epfl ch OLTP Wust J Boese J H Renkes F Blessing S Krueger J amp Plattner H 2012 October Efficient logging for enterprise workloads on column oriented in memory databases In Proceedings of the 21st ACM international conference on Information and knowledge management pp 2085 2089 ACM 94 The Pyrrho Book May 2015 Appendix 1 Using ADO NET for various databases In this lab we review simple database application development using C and ADO NET In each case we will use a simple sporting club as a model For simplicity we will work with an individual sport such as table tennis or squash Member id int primary key firstname char surname char Played id int primary key playedon date winner int references member loser int references member agreed Boolean If all of the players are able to modify this da
311. se does not change much for values of N between 4 and 32 For ease of drawing the illustrations in this section show N 4 The BTree itself contains a root Bucket and some other data we discuss later Root inner The BTree dynamically reorganizes its structure so that apart from the root all Buckets have at least N 2 Slots and at each level in the tree Buckets are either all Inner or all Leaf buckets so that the depth of the tree is the same at all values Leaves The basic operations on B Trees are defined in the abstract base class ATree lt K V gt ATree lt K V gt Add ATree lt K V gt Remove etc Static methods are used for most operations because in almost all cases a new header structure is created if anything is modified according to principle 2 2 3 So for example to add a new entry to a list of tables we have code such as CTree lt string DBObject gt Add ref tables name tb The basic format here is ATree lt K V gt Add ref Tree Key Value For a multilevel index Key can be a Link this is implemented in MTree and RTree see section 3 2 The following table shows the most commonly used operations Name Description long Count The number of items in the tree object this key Get the value for a given key bool Contains key Whether the tree contains the given key SlotEnumerator lt K V gt Enumerates the pairs in the B tree GetRowEnumerator 33 The Pyrrho Book May
312. sec 4 3 6 A textfile containing rows for a table can similarly be added using a command such as insert into directors values rowsfile Simple data can be provided in a csv or similar file The first line containing column headings and exposed spaces in the file are ignored Data items in the given file are separated by exposed commas or tabs Rows are parenthesized groups optionally separated by commas or provided without parentheses but separated by exposed semicolons or newlines Characters such as commas etc are not considered to be separators if they are within a quoted string or a structure enclosed in braces parentheses brackets or pointy brackets Of course if the file is really called rowsfile txt you need to say so rowsfile txt 2 You can also use the REST service there is a RESTclient in the distribution to POST csv data to a table However this only works for tables that have a primary key For this service don t post the first line of a csv file since this contains column headers Don t forget to run the OSP server as administrator if you get the Access denied message on start up the REST service will not be available 3 You can copy data from one table to another by using the INSERT SELECT combination as in insert into mytable select somecolumn anothercolumn from anothertable 4 You can get PyrrhoDB to draw charts if you want You can add metadata to tables and columns There is a blog post about th
313. sed in single or double quotes but may contain string literals that are enclosed in quotes xmIname represents a case sensitive sequence of letters and digits iri is an IRI enclosed in lt gt and xml represents any Xml content not including an exposed or In SQL all string literals are enclosed in single quotes case sensitive identifiers or containing special characters are enclosed in double quotes A6 1 Statements Sql SqlStatement SqlStatement Alter BEGIN TRANSACTION WITH PROVENANCE string Call COMMIT CreateClause CursorSpecification DeleteSearched DropStatement Grant Insert Rename Revoke ROLLBACK SET AUTHORIZATION CURATED SET PROFILING Value SET ROLE id FOR DATABASE id SET TIMEOUT int UpdateSearched HTTP HttpRest The above statements can be issued at command level You SELECT multiple rows from tables using the CursorSpecification Inside procedures and functions there is a different set Note that direct SQL statements are in both lists Apart from SET ROLE the above SET statements are available only to the database owner SET AUTHORIZATION CURATED makes all further transaction log information PUBLIC it is not reversible Statement Assignment 181 The Pyrrho Book May 2015 HttpRest Call CaseStatement Close CompoundStatement BREAK Declaration DeletePositioned DeleteSearched Fetch ForStatement GetDiagnos
314. select from _ we merge the results of the query on each server in L That is From x is replaced by Union From x Union From x similarly to other partitioned tables 9 4 Connection Management At the moment the connection string names a Pyrrho server default localhost a Pyrrho port by default 5433 and one or more databases and assumes that its Windows user credentials will be understood by that server That server however might have no local data and act merely as a client to other servers that can locate the data connections it really requires For now let s consider the linked notions of configuration connections and transactions 1 The server has a list of configured local and remote databases masters stores that it knows about and it also allows local unconfigured databases to be accessed and created At this stage and for any newly defined database initial loading occurs For a full database this includes recreation of database objects such as indexes for a master it includes verification of distributed transactions for storage it includes syncing with the master if remote and for a remote database it involves none of these things 2 If any of these configured servers are offline the server will retry in 10 seconds and will continue to retry but the interval doubles on every retry 85 The Pyrrho Book May 2015 3 When a client connects to one or more databases it supplies some extra information
315. sesernadeuy aug duty teatuc da AS 210 Appendix 10 Pyrrho s Connection String coomommmmmsissmsss 211 ES AAA E d ne etn TL en ER ESP rn eS ee ne eee Pe ener oer nee eee eee 213 The Pyrrho Book May 2015 Chapter 1 Introduction to the Book This book focuses on a number of aspects of database management systems that are important in real life application but in which current products fall short of what is required The book will make a contribution to DBMS design by suggesting a number of fundamental improvements to DBMS architecture and validating them by means of a working proof of concept DBMS Pyrrho that includes not just the basic relational model but most of the features of ISO standard SQL and some other suggestions from the database community We will discuss the trade offs in speed and complexity involved in including these features over the years the set of additional features offered by Pyrrho has changed with some advanced features RDF SPARQL JPA client side data models etc being removed from Pyrrho where the added complexities have not justified themselves In this book supporting data consistency is a prime concern In particular it should not be the application s responsibility to maintain consistency or to clean up after errors The DBMS should have the task of ensuring that data is consistent and constraints as defined in the schema are maintained While databases should be fast and scalable 100 accuracy is more
316. start to Request _ 127 0 0 1 6 Enter to Continue EN tos ting D 7 127 0 0 1 54 About to Begin D 7 Enter to Continue D 7 Enter to Continue it ge Flush comple osp len 1142 3 for D 7 Enter B D osp len 179 to start 127 0 1 5434 6 Enter to Continue to Continue to start to s Home Share View ate table E F int pri H DATA E A gt insert into E values 4 7 Database valu 1 5434 Student fi password Osp D osp lt 2 items f 3 a Ts z mS D DATA E B 0sp D osp 2 We see that on completing Phase 4 for _ B has removed the temporary transaction file in folder B Press Enter twice more to complete the transaction and get the SQL gt prompt in the PyrrhoCmd window EN Command Prompt osp T p 5434 d A s 0 S 0 Command Prompt OSP T d B p 5435 s 0 S 0 M 0 bStorage Flush complete for _ _ 127 1 5434 974 _ a 974 osp len 105 2 for _ 9 Enter to start to Request _ 127 0 0 1 5 Enter to Continue e 3 for _ 5 Enter to s Connecting D 7 127 0 0 About to Begin D 7 Enter to Continue d D 7 Enter to Continue mit for _ osp at 974 Flush complete for _ osp len 1142 for D 7 Enter to start Flush complete for D osp len 179 _ 9 Enter to 1 5434 6 Enter to Continue to Continue 4 for D 7 Enter _ 9 Enter to s Committed OSP gt PyrrhoCmd p 5434 D ISQL gt create tabl
317. start parsing e g a procedure body using the owner role for the functions and structures concerned Changes installed at level 3 of the database affect the SqlDataTypes The DataTypeTracker currently can be used to find the data type at a previous version of the database as this is needed for reading any data in the data file All SqlDataTypes used for persistent data are located in the PhysBase They should not be stored anywhere else However a during a transaction each intermediate result has an SqiDataType b each database knows what standard data types are persisted in that database For rapid type identification SqlDataTypes can be looked up in two indexes one for all types in use in the transaction ToString gt bool and one for persisted types for each PhysBase known to the server each PhysBase has types ToString gt defpos c each role has an index of named domains defined in that role namedDomains name gt defpos Note that the CompareTo function for SqlDataTypes is based on ToString which does not include either pbname or defpos thus SqlDataTypes can be considered equal for assignment etc but may need to be reified for a particular database if the value is made persistent 37 The Pyrrho Book May 2015 The following well known standard types are defined by the SqlDataType class Name Description Null The data type of the null value
318. stems 6 p 213 226 Laertius Diogenes 3 cent The Lives and Opinions of Eminent Philosophers trans C D Yonge London 1895 Lessner T Laux F Connolly T Crowe M 2012 Transactional Composition and Concurrency Control in Disconnected Computing nternational Journal of Advances in Software 4 p 442 460 Mensac D A Nakamishi T Optimistic versus Pessimistic ConcurrencyControl Mechanisms in Database Management Systems nformation Systems 7 p 13 27 Moorthy M K Seetharaman A Mohamed Z Gopalan M amp San L H 2011 The impact of information technology on internal auditing African Journal of Business Management 5 9 3523 3539 Moreau L 2010 The foundations for provenance on the Web Now Publishers Inc Oh S Park S 2003 Task role based access control model Information Systems 28 p 533 562 Ouyang X Nellans D Wipfel R Flynn D Panda D K 2011 Beyond block I O Rethinking traditional storage primitives High Performance Computer Architecture HPCA 2011 IEEE 17th International Symposium on pp 301 311 IEEE doi 10 1109 HPCA 2011 5749738 Raab F Kohler W Shah A 2001 Overview of the TPC C benchmark The Order Entry Benchmark Transaction Processing Performance Council www tpc org SQL2011 ISO IEC 9075 2 2008 Information Technology Database Languages SQL Part 2 Foundation SQL Foundation ISO IEC 9075 4 2008 Information Technology Databa
319. string is also available see section 8 1 ScriptConnect ScriptReader TransactionConfli DatabaseError The action attempted has conflicted with a ct concurrent transaction e g two users have attempted to update the same cell in a table The changes proposed by the current transaction have been rolled back because the database contents have been changed by the other transaction Class Subclass of Description PyrrhoTable PyrrhoTable lt T gt PyrrhoTable PHP support Class Subclass of Description Provided for PHP support section 6 7 Provided for PHP support section 6 7 206 The Pyrrho Book May 2015 A9 1 DatabaseError The methods and properties of DatabaseError are Method or Property Explanation Dictionary lt string string gt info Information placed in the error the keys specified in the SQL standard are CLASS ORIGIN SUBCLASS ORIGIN CONSTRAINT_CATALOG CONSTRAINT_SCHEMA CONSTRAINT_NAME CATALOG_NAME SCHEMA_NAME TABLE_NAME COLUMN_NAME CURSOR_NAME MESSAGE_TEXT Pyrrho adds PROFILE_ID if profiling is enabled The reason for the exception inherited from Exception this can be localised as described in section 3 8 String SQLSTATE The signal sent from the DBMS usually a five character string beginning with a digit such as 2NO00 Many of these codes are defined in the SQL standard String Message A9 2 Date The methods and properties of Date are
320. such a session will be added to the first named database while objects in the other databases remain accessible subject to the permissions that have been granted to the user Connections can be opened and closed for very little cost since the database file is only fully processed the first time the server accesses it For example a connection list is of form Files A B C D would be appropriate for a connection for performing some sort of data analysis on database D using tools stored in database C where database B contains partially completed analyses and database A is being used for temporary results that will be deleted at the end of a session Database B can be archived and a fresh analysis database constructed for the next period of analysis while the tools in C are kept under revision for future use separate from the live database D By default only the first file in a connection can be modified using the connection see section 2 8 3 With this scenario connections of form Files D would be used for normal business operations on D connections of form Files C D would be used for adding new tool objects such as stored procedures or views useful for data analysis and connections of form Files B C D would be used to create the analysis tables B and C would probably not be usable on their own The ordering of files is the search order when resolving names of database objects In the absence of name conflicts Files A
321. t to CheckSerialisation _ 127 0 0 1 5435 14 Enter to Continue 1 5 for D 13 Enter to start 1 5 for D2 15 Enter to start to CheckSerialisation D2 13 Enter to Continue 2 for _ 12 Enter to start DbStorage Flush complete for A _ _ 127 0 1 5434 974 127 0 1 5435 hase 2 for D 13 Enter to start Bl IA En O x EN Command Prompt PyrrhoCmd p 5434_ d Home Share View t E DATA E gt A L _ _Q127 0 0 1 5434 974 _ 0127 0 0 1 543 D osp Student And Enter saves a similar file for D EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 O X 5 daB s0 S0 M 0 1 for D 13 Enter to start 1 for D2 15 Enter to start to Prepare D2 13 Enter to Continue to CheckSerialisation D2 13 Enter to Continue 1 for _ 17 Enter to start to Prepare _ 127 0 0 1 5435 14 Enter to Continue to CheckSerialisation _ 127 0 0 1 5435 14 Enter to Continue 1 5 for _ 12 Enter to start 1 5 for _ 17 Enter to start to CheckSerialisation _ 127 0 0 1 5435 14 Enter to Continue gt 1 5 for D 13 Enter to start 1 5 for D2 15 Enter to start to CheckSerialisation D2 13 Enter to Continue 2 for _ 12 Enter to start DbStorage Flush complete for A _ _ 127 0 0 1 5434 974 127 0 0 1 5435 974 D 248 D2 39 osp len 155 Phase 2 for D 13 Enter to start DbStorage Flush complete for A D _ 127 0 0 1 5434 974 127 0 0 1 5435 974 D 248 D2 39 osp len 235 Phase 2 for D2 15 Enter to start Billa O X E Command Prompt P
322. t Level 4 of the code The Pyrrho Book May 2015 10 11 12 23 The aim of SQL query processing is to bridge the gap between bottom up knowledge of traversable data in tables and joins e g columns in the above sense and top down analysis of value expressions Analysis of any kind of query goes through a set of stages a source analysis to establish where the data is coming from b selects analysis to match up references in value expressions with the correct columns in the sources c conditions analysis which examines which search and join conditions can be handled in table enumeration d ordering analysis which looks not only at the ordering requirements coming from explicit ORDER BY requests from the client but also at the ordering required during join evaluation and aggregation and finally e RowSet construction which in many cases can choose the best enumeration method to meet all the above requirements As a practical matter it is convenient to allow multi database connections For example this facilities analysis or modelling of a database using temporary tables without adding such temporary tables to the business database However if a transaction in such a connection causes changes to more than one database this causes a permanent linkage recorded in both databases and all linked databases must always continue to be available to any server that is using any of them While such multi database transactions are support
323. t to Begin D 11 Enter to Continud Home Share View T DATA E A Name osp Server C immediately opens a connection to B in order to synchronise D B in turn will check it is synchronised with A In B s window press Enter once E Command Prompt osp T p 5434 d A s 0 S 0 BN Command Prompt OSP T d B p 5435 s 0 S BN Command Prompt OSP T d C p 5436 s 0 S 0 M 0 DbStorage Flush complete for B _ _ 127 0 Phase 3 for _ 5 Enter to start Connection 6 Coordinator A 436 Flconnecting D 5 127 0 0 1 5435 Connecting D 9 127 0 0 1 5434 About to Begin D 5 Enter to Continue About to Begin D 9 Enter to Continue startCommit for _ osp at 974 i 6 Protocol byte RemoteBegin DbStorage Flush complete for C _ osp len 1142 4 Protocol byte RemoteCommit hase 3 for D 7 Enter to start StartCommit for _ osp at 1137 Phase 3 for _ 9 Enter to start PbStorage Flush complete for B _ osp lenlabout to Commit _ 127 0 1 5435 6 Enter to Continue 4 Ends with 31 Closed _ 127 0 0 1 5435 6 Enter to Continue 6 Protocol byte CloseConnection Phase 4 for _ 5 Enter to start i Phase 4 for D 7 Enter to start Closed D 5 Enter to Continue bout to Close D 9 Enter to Continue Phase 4 for _ 9 Enter to start Closed D 9 Enter to Continue 1 tid 1 Committed 6 Ends with 9 1 Ends with 1 Connection 8 Coordinator 127 0 0 1 5436 F Connection 5 Files D User asusrog Student ilconnecting D 11 127 0 0 1
324. tabase folder Connection 1 Files _ User 5434 d A 5 1 Protocol byte ExecuteReader Pyrrho DBMS c 2015 Malcolm Crowe and Uni T an 435 S 0 M DbStorage Flush complete for 5 2 19 March 2015 www pyrrhodb com B p 5435 s 0 S M 0 Enter to 3 Coordinating Commit for tid PyrrhoDBMS protocol on 127 0 0 1 5434 Pyrrho DBMS c 2015 Malcolm Crowe and Un Reconfigure _ Database folder A 2 19 March 2015 www pyrrhodb com Phase 1 for _ 4 Enter to start Connection 2 Coordinator Phase 1 5 for _ 4 Enter to start 2 Protocol byte RemoteBegin About to Begin D 3 Enter to Continue Phase 2 for _ 4 Enter to start 2 Protocol byte CloseConnection Closed D 3 Enter to Continue Phase 3 for _ 4 Enter to start Exception 00000 PyrrhoDBMS protocol on 127 0 0 1 5435 StartCommit for osp at 34 2 Rollback atabase folder B bStorage Flush complete for osp len 2 Ends with 9 Connection 2 Coordinator 127 0 0 1 54 4 Enter to start Connection 4 Coordinator 127 0 Committed 4 Protocol byte RemoteBegin Connecting D 5 127 0 0 1 5435 OSP gt osp T bout to Begin D 5 Enter to Continue Share View RIE OSP gt PyrrhoCmd p 5436 _ SQL gt insert into _Database values D 127 0 0 1 5436 2 password 127 0 1 5435 student DATA E A lpassword p 5434 d A s S M 0 IE OSP gt OSP T d B p 5435 s S 0 T 54 A s S 0 M 0 Enter to star T d B p 5435 s 5 0 M 0 Enter Pyrrho DBM
325. tabase they may well be problems with people putting in incorrect details in the played table For now we simply focus on writing simple programs that access and modify this data The details of the above description will change a bit as we work with different DBMS You will need to install Visual Studio C or Professional which you can get from DreamSpark These notes assume Visual Studio 2012 but really they are all very similar A1 1 MySQL We begin with MySQL downloaded the web community installer from http www mysal com downloads Choose the options for development There is no need to download Connector NET separately Start up the MySQL Command Line Client On the VM provided on our Hyper V server the password is MySQL_123 mysql gt create database mydatabase mysql gt use mydatabase mysql gt create table member id int primary key firstname varchar 20 surname varchar 20 mysql gt insert into member values 56 Fred Bloggs mysql gt insert into member values 78 Mary Black mysql gt select from member mysql gt create table played id int primary key playedon date winner int references member loser int references member agreed boolean mysql gt insert into played values 32 2014 1 9 56 78 false Now that we have a database and some tables let s construct a database application that accesses it made sure had a folder called C Temp and then created a Visual C Win
326. te in the playedon field the date format is dd mm yyyy the other way round from MySQL 5 Now double click the Database1DataSet and drag the Members table onto it 6 This time when you add the DataGridView click Choose Data Source and browse down to get Database1DataSet gt Member If you now view code you will see that a member table adapter already has been configured to load the data into the DataGridView 7 As before we need to implement a way of updating the database This time the code we want in RowValidated is memberTableAdapter Update database1DataSet Member 8 Once again add the two gadgets we had in the last tutorial a textbox and a combobox The code of the textbox is identical to the previous time 9 For the comboBox we can set up the Items as follows comboBox1 Items Clear var rdr database1DataSet CreateDataReader while rdr Read comboBox1 Items Add rdr 1 ToString 10 We can modify this as before to get the key values for an item 98 The Pyrrho Book May 2015 o clubSQL Running Microsoft Visual Studio Quick Launch Ctrl Q P x FILE EDIT VIEW PROJECT BUILD DEBUG TEAM SQL TOOLS TEST ANALYZE WINDOW HELP o LF anno ta n OS DatabaselDataSet xsd Form1 cs Design 4 3 clubSQL Form1 O comboBox1_SelectedValueChanged object sender EventArgs e if dataGridView1 SelectedCells Count gt textBox1 Text dataGridViewl SelectedCells 0 Value ToString x a9 Form1 amp
327. te modified osp D osp lt items 1 item selected 179 bytes BE amp Ec B t E DATA E C Name _0sp And further Enters for B s and C s windows to complete the transaction At this point B is once again synchronised with A Most of short lived connections in this narrative are simple handshakes to get database length Distributed databases win out when large data sets and effective indexes are stored close to where they are needed and the ratio of reads to writes is favourable If there are a lot of writes to big data partitioned database are indicated since each partition can have its own master and replication can often be avoided 158 The Pyrrho Book May 2015 Appendix 5 Partitioned Database Tutorial The exercise follows the blog at http pyrrhodb blogspot com just with more detailed instructions In both this and the Distributed Database Tutorial it is important to realise that the very complex distributed transactions documented here mostly happen when the database is reconfigured With good design most normal operations on the distributed or partitioned databases will not require distributed transactions They will in general involve some synchronisation between the transaction master the replication hosts and or base database but full 3 phase commit only occurs when data on two or more databases or partitions are changed in a single transaction and this will be relatively unusual This versi
328. tem Name the server runs on just one core 2 26300 The TPCC benchmark is designed to s2152 behave badly with concurrency since the 30528 next order number is a bottleneck Total 10300 throughput of the benchmark is lower an with 2 terminals because of transaction sua conflicts but then increases slowly as Execution Status more terminals are added can use the CPU more by running multiple concurrent terminals with 5 the CPU usage reaches 57 The TPCC application in the open source distribution has tabs for the various functional tests of Tpcc but for the purposes of database tuning the two most interesting are Setup and New Order pictured The Setup page allows you to decide how many warehouses and contains buttons for creating the database its list of products the districts with their lists of customers and the warehouses with their stock The product descriptions and customer names and addresses are all generated according to randomising rules in the TPCC specification parameters such as tax are also randomised according to the specification All of this takes around ten minutes on a PC for a single warehouse and the database is initially 110MB You can observe the progress of building the database by using a command window PyrrhoCmd Tpcc and then at the SQL gt prompt table RoleSTable shows the number of rows that have been set up in each table If the server is shut down and restarted it takes about a minute for
329. ter of life and death To ensure serialisability we must conclude that A x and C y will conflict if A x affects the value of a Boolean expression used by C i e if quantity x 101 and description x like y In this scenario a conflict will also be detected if C actually updates the price used by A As aresult of these considerations the conflict implementation rules require that changes made since the start of a transaction are checked for conflict with anything read by the transaction Suppose that C starts before A starts but A starts and commits before C attempts to commit Then C will fail because one of the quantities read by C has changed If C commits first then A will fail if x s price has changed 5 2 Transactions and Locking Protocols In chapter 2 we saw an introduction to the detailed operation of Pyrrho s optimistic transaction mechanism The main commercial database systems use pessimistic locking protocols The normal argument in favour of locking is that once locks are acquired a correctly formed transaction can be guaranteed to complete whereas an optimistic system might have to start over having done some work However in pessimistic system the process of acquiring locks can be lengthy and may require the application to release its locks and start again Years ago there was a lot of debate in both directions with many research papers claiming that optimistic methods result in higher throughput 44 The Pyrrho Boo
330. the database to be read in from disk so if you start up the TPCC application you may have to wait this long before the window appears The NewOrder page has two useful buttons Run will run 2000 new orders and this will take one or two minutes The Step button allows you to see how a single order is built up Each step models an action of the clerk to select a district a customer an item a quantity entering them in the white parts of the screen and shows the responses from the database in the yellow parts of the screen It is not wise to use a single benchmark for performance tuning But since it includes quite large data sets this particular benchmark can be used with a database engine to investigate what happens to network traffic it is a huge advantage to use fixed size blocks what is the best size for BTree buckets this hardly matters whether minimising disk reads is worthwhile 5 what enumeration optimisation can be done 3 for a constant key shortcut will a specific index class for integer keys work better than a generic one no what is the cost of database features such as multiple database connections 1 whether only using one kind of integer internally would help no etc 2 7 Pyrrho s internal structure The database file contains is the transaction log and this gets read in its entirety when the database is loaded following a restart of the database server cold start Each database is in a separate file The data
331. the operating system and tasks requiring them are kept in numerous queues for system locks For example in C a program needing a resource whose lock is called MyLock say will wrap a section of code with a declaration such as lock MyLock and then execution halts at the lock request until the resource is available and the lock is released at the end of the critical section 4 2 TCP IP services For other things that aren t at quite such a low level a server process manages a request queue A very popular way of doing this is to use TCP IP Each server is assigned a port on which it listens for requests for its service When a client sends a message to this port the TCP mechanism creates a two way communication channel using a new server port for subsequent communication in that session Messages on this 2 way channel will generally follow an application defined protocol of request and response maybe including callbacks and exception handling All operating systems have limits on the number of ports that can be open at any time so it is important for the TCP channel to get closed as soon as possible This will happen if either the client or server process terminates but obviously it is important not to wait until then Many application protocols are designed to be very short term A Web service lasts only as long as it takes to respond to a single request from the client An email service remains connected just for long enou
332. the syntax file host port user role And the connections string can be compound using a Json like notation see below By default only the first database in a multi database connection is modifiable using the connection but the Modify flag is available for changing this behaviour In addition a Role can be specified per database The syntax of ConnectionString is similar to ADO NET ConnectionString Setting Setting Setting id val val The possible fields in the connection string are as follows Field Default value Explanation Base Used by server server communication to create a new partition remotely Not for client server use Used in server server communications the transaction coordinator server One or more comma separated database file names excluding the pfl or osp extension Characters within names are not allowed If the only field in the connection string is Files the prefix Files can be omitted Host 127 0 0 1 The name of the machine providing the service Coordinator Files Locale The name of the locale to be used for error reporting The default is supplied by the NET framework Modify The default value is true for the first file in the connection and false for others If the value true is specified then it applies to all of the Files in the current connection string Port 5433 The port on which the server is listening Provider PyrrhoDBMS Role databasename Ar
333. there are about 40 different types of record for specifying domains columns tables procedures and for setting up and modifying roles and security permissions Any database object or record can be referred to by its defining position The name of an object thus becomes metadata and can be changed or made role dependent so that the same object can be named differently by different roles Most of the records will contain data for the base tables All of these are binary records that do not depend on the machine data formats for the platform used apart from the basic concept of octet Character data uses Unicode UTF 8 encoding Integers are represented in the data file as sequences of octets corresponding roughly to base 256 arithmetic The maximum integer allowed has 2048 bits Numeric data is defined by two such integers for mantissa and power of 10 scale Blobs binary large objects are stored in the data file like any other data as an integer possibly a very large one followed by the blob data as a list of octets All dates and times use universal time This design brings many benefits as briefly mentioned in the above account platform and locale independence the ability to refer to a database object by its defining position Most importantly this simple transaction log design of the database gives a natural automatic serialisation of transactions The data file represents level 1 of the Pyrrho engine At level 2 Physical the design consists
334. this section compares with corresponding features in IBM s SolidDB and Microsoft s SQL Server Pyrrho always supplies a pseudocolumn in all base tables called CHECK The value is a string that includes the transaction log name defining position and current offset of the row version When retrieved it refers to the version valid at the start of the transaction but it can be used at any time subsequently inside or outside the transaction to see if the row has been updated by this or any other transaction this is the only violation of transaction isolation in Pyrrho There is a method in the PyrrhoConnect subclass of IDbConnection for verifying a check string bool Check string ch Check to see if a given CHECK pseudocolumn value is still current i e the row has not been modified by a later transaction Unlike other DBMS the check cookie is just a note of a transaction log position and so is persistent In IBM s solidDB the concurrency control mode can be set per table using the ALTER TABLE t SET OPTIMISTIC PESSEMISTIC statement or for all tables using the General Pessimistic setting in solid ini With the default optimistic setting 1 Each time that the server reads a record to try to update it the server makes a copy of the version number of the record and stores that copy for later reference 2 When it is time to commit the transaction the server compares the original version number that it read against the versio
335. tic locking the first sign of failure may well be when the transaction tries to commit A transaction will fail if it tries to make a change that conflicts with a change made by another transaction In both cases it is important for database applications to be prepared to restart transactions In the case of pessimistic transactions this would normally follow deadlock detection or timeout With pessimistic locking an attempt could simply be made to re acquire the same locks this step could be performed automatically by the server However it is not good practice for the transaction s sequence of SQL statements to be simply replayed since generally the state of the database will have changed this is why the transaction failed and the application should start again to see what to do in this new situation In the classic transaction example of withdrawing money from a bank account a transaction for making a transfer might include an SQL statement of the form update myaccount set balance balance 100 or update myaccount set balance 3456 Writing SQL statements in the first form makes them apparently easier to restart but the point being made here is that it should be the client application s responsibility to decide if the statements should simply be replayed on restart The server should not simply make assumptions about the business logic of the transaction Pyrrho transaction checking includes checking that data read by the transac
336. tics IfStatement Insert ITERATE label LEAVE label LoopStatement Open Repeat RETURN Value ROLLBACK SelectSingle Signal UpdatePositioned UpdateSearched While HTTP HttpRest ADD UPDATE url_ Value data_Value AS mime_string DELETE url_Value Here ADD and UPDATE are used as the SQL analogues of POST and PUT For Http GET see Value By design in Pyrrho the execution of ROLLBACK causes immediate exit of the current transaction with SQLSTATE 25005 and premature COMMIT is not supported so that while ROLLBACK is in both lists above COMMIT is nly in one A6 2 Data Definition As is usual for a practical DBMS Pyrrho s Alter statements are richer than SQL2011 Alter ALTER DOMAIN id AlterDomain ALTER FUNCTION id Parameters RETURNS Type AlterBody ALTER PROCEDURE id Parameters AlterBody ALTER Method AlterBody ALTER TABLE id AlterTable ALTER TYPE id AlterType ALTER VIEW id AlterView Procedures functions and methods are distinguished by their name and arity number of parameters Method MethodType METHOD id Parameters RETURNS Type FOR id Parameters Parameter Parameter 182 The Pyrrho Book May 2015 Parameter id Type The specification of IN OUT INOUT and RESULT is not yet supported MethodType OVERRIDING INSTANCE STATIC CONSTRUCTOR The default method type is INSTANCE All OVERRIDING methods are instance methods
337. tion has not been changed by another transaction 5 1 A scenario of transaction conflict To simplify the discussion let us consider operations on a table Products Products id int primary key description char quantity int check quantity gt 0 price int In this system some transactions will involve a purchase failing in the absence of sufficient stock 43 The Pyrrho Book May 2015 A x SELECT price FROM Products WHERE id A x UPDATE Products SET quantity quantity 1 WHERE id A x Some transactions will request several items failing if any item is unavailable B X1 X2 Xn BEGIN TRANSACTION A x1 A X2 A Xn COMMIT Now for normal levels of activity these transactions execute very rapidly and concurrency is not likely to be a problem In order to have problems with transaction failures we need to assume huge transaction volumes a huge size to the Products table or that the Products table is geographically distributed over many servers etc So assuming that we can imagine transaction conflict occurring at all we note that transactions of type B X1 Xn will conflict with any concurrent A x where x x some i Other transactions will involve adjustments to the stock levels or prices For example we might implement a policy of discounting plentiful items whose description matches a given pattern e g BOLT C y UPDATE Products SET price price 0 9 WHERE quantity gt 40 AND description like C y This transa
338. tion only need connect to that partition but generally a multi file connection will be required For example alteration to a table which references the base partition will require a connection that includes the base partition Note that many cross partition operations in the logs will be treated as cross database transactions and the server will try to verify coherence of the participating databases 90 The Pyrrho Book May 2015 Schema information should be in the root database so tables should be initially created there A new partition can be configured to contain existing data this data will then no longer be available in the base database It is possible to add a new empty partitioned table to an existing partitioned database Pyrrho servers can be configured to do this automatically in response to increases in database traffic 10 3 Database Partitioning Suppose that one of the tables on a database has so much traffic that it is worth while placing a part of it on a different server and then this part should be chosen to minimise the number of transactions that access both parts of the table Then single partition transactions can be dealt with by the partition server which is the transaction master for its data It needs only to check with the base server only that the schema has not changed Cross server transactions will be slower Schema changes need to be done in the base database so they can be notified to partitions this include
339. tions to the database Such database systems are said to be server based client server database systems a program that needs to access the data in the database opens a connection to the server and uses a standard protocol to send and receive the data it wants One of the main topics in this course will be the ways that the DBMS ensures consistency and integrity in a busy database system and is as available as possible Some computer programs use local databases that is there are no other programs that need to access the data while it is in use Such database systems are often called embedded For example many devices today phones cars fridges etc have computer systems that use local databases With HTML5 we have ways for web pages to have local data Many important pieces of information in a company are not stored in databases however It is fairly rare for spreadsheets web pages or office documents to be stored in the database Instead these are stored in the file system as ordinary files Strangely although such individual files are commonly security protected in company computer systems and shared explicitly among user groups most companies still apply security in an all or nothing way the entire database and not to the separate types of data inside it despite the availability of security facilities in the database management system This is yet another aspect we will look at in this module as it would seem that the security facilities
340. uc adoos 36 MAR ACTE TO a ea laa a e el 36 The Pyrrho Book May 2015 DOCM iS is 36 Dad Pd tas 37 Chapter 4 Database Servers sscsssssssssssssssssssssssssssssssossesssscsssoscssssasesssasecssasesenesesenasessnes 39 4 1 Servers ANG SELVICES situntiidaidad eats 39 4 2 TCP IP Ser dla 39 4 3 The application protocol iy ceicssassdeeccisvescesasacecessavansceasedencvsncasaatededenecesnavcava le deesteauedaceane 40 ACA A O 40 NA 40 46 Database CONCHITENCY sssxcctnaclacial rosserae ri lne een eo eon tebe has eae aan eae 41 4 7 Databases and the file system siii cccesaledesatacvssuecasdacedenspavadta hausnccessaccavasteseceedeonacdene 41 4 39 Alternative AUG MILE CULES sicuris ae e e dese acadshe sede aE ET 42 Chapter 5 Locking vs Optimistic Transactions s eesssesssecsscecesocesocessoesssecssocesoossoosesseesseee 43 5 1 A scenario of transaction conflict assi aiii lic 43 5 2 Transactions and Locking POCO a 44 Da OMAP SHOE TSO LATION E 45 5 4 Transaction Masters nenei a A E onses 46 5 5 ADO NET and Transact ONS dE Toei SDE 47 O SES UOTE oh fate hcl lee pale I coc lege Ed OG 47 Dal rams actiom PIOMUNG 64 oo5 ech ie e EE 48 IS Prol mmplementation ssia a ae eee eee SS 49 5 9 PyrrhoDBMS safe optimistic transactiONns ceesceceeececssececseececeeeeeceeeeesseeeeneeeeaas 50 Transaction Conflicts sonenn nahi bate aa E E R vetetarasaon es 51 Entity Itrip nati 51 RGferential Integrity anniina ai aaia a a 52 Chapter 6
341. unt Text rdr 0 rdr Close Account HE Action else Balance Amount Text 0 00 a CancelButton IsEnabled true dede g 50 00 From private void Account2_DropDownOpened object sender EventArgs e gt Cash Account if selected null Fist var cmd db CreateCommand cmd CommandText select accno custname from accounts Account2 Items Clear var rdr cmd ExecuteReader while rdr Read if rdr GetInt32 selected id Account2 Items Add new AcInfo rdr GetInt32 rdr GetString 1 rdr Close private void OKButton_Click object sender RoutedEventArgs e AcInfo sub bool PayOut IsChecked selected bool PayIn IsChecked other AcInfo add bool PayIn IsChecked selected bool PayOut IsChecked other try var tr db BeginTransaction var cmd db CreateCommand if sub null cmd CommandText update accounts set balance balance Amount Text accno sub id cmd ExecuteNonQuery if add null 27 null null where The Pyrrho Book May 2015 cmd CommandText update accounts set balance balance Amount Text where accno add id cmd ExecuteNonQuery z Fi tr Commit An net Balance IsChecked true am Cash IsChecked true gt Per Account2 SelectedIndex 1 Pay Out Account1_SelectionChanged sender null 10000 00 catch Exception ex To Cash Status Content
342. urable transaction commits Recent work from Microsoft Google and IBM supports optimistic transaction management by using versioning e g Garus 2012 Guenther 2012 IBM 2011 and this represents a big change from always using locking protocols In fact optimistic transaction management is the default in Microsoft s Entity Framework Google s Datastore and IBMs EJB implementations At first sight the requirement at the Internet level for optimistic transactions seems fundamentally at odds with the requirement in the large commercial database systems to use locking protocols Numerous papers e g those cited above provide complex workarounds but for many purposes the difficulties are not as severe as might be expected The first reason is that internet applications deal directly with databases on behalf of their multiple users as far as the database is concerned there is only one client Similarly the databases at the heart of messaging systems have only one client namely the enterprise server and different enterprise servers Exchange BizTalk WebSphere etc use different databases The second is that concurrent access to the database is often limited by tuning arrangements In many DBMS there may be parallel transactions but the steps in these transactions are serialised by the TCP request socket mechanism few DBMS use multi threading at the step level As we have seen Pyrrho s multithreading is at the connection level and assume
343. ut he wants more reader friendly names and to hide these numeric columns So add a new role for the Librarian and allow Fred the admin option so he can define his preferred column headings create role librarian grant all privileges on author to librarian grant all privileges on book to librarian grant librarian to COMP10059 Fred with admin option el rrio SRL tec sn M1 Cubs Lina Cae ode Baa grand all jabe ae autos fo Meri grand AD porra oe beak do bbraras grant brent TORE ad with wirin option A generation rule in SQL2011 is not allowed to contain a query expression Otherwise there are no Pyrrho extensions here Fred can now log in to the system with his Librarian role With the PyrrhoSQL client shown below we make sure Fred login with the LIBRARIAN role selected from the drop down If he uses the command line then after starting with pyrrhocmd Library he needs 62 The Pyrrho Book May 2015 set role librarian or he won t see much He decides to rename some columns this is a Pyrrho extension define a new column called Availability and to create a role for his readers with a simpler table structure alter table book alter aid to Authorld alter table book alter aname to Author alter table book alter title to Title alter table book add Availability boolean default true select Title Author Availability from book Hot hac fori MJS Deuba Library alter as bot alter ed ho Athor ai
344. uteReader returned data as in IDataReader PyrrhoReader Initiates a database SELECT and returns a reader for the ExecuteReaderCrypt returned data as in IDataReader The results are not encrypted object ExecuteScalar Initiates a database SELECT for a single value object ExecuteScalarCrypt Initiates a database SELECT for a single value int ExecuteNonQuery Initiates some other sort of Sql statement and returns the number of rows affected Int ExecuteNonQueryCrypt Initiates some other sort of Sql statement and returns the number of rows affected A9 6 PyrrhoConnect Depending on the Pyrrho version PyrrhoConnect implements or imitates the IDbConnection interface and supplies some additional functionality Method or Property Explanation int Act string sql Convenient shortcut to construct a PyrrhoCommand and call ExecuteNonQuery on it Activity activity AndroidOSP Set only Set the Activity into PyrrhoConnect This must be done before the connection is opened E g in Activity OnCreate bundle use code such as conn new PyrrhoConnect Files mydb conn activity this conn Open Note that mydb without the osp extension needs to be an AndroidAsset to be copied to the device PyrrhoTransaction Start a new isolated transaction like IDbTransaction BeginTransaction bool Check string ch Check to see if a given CHECK pseudocolumn value is still current i e the row has not been modified by a late
345. val precision that can include any fields other than YEAR or MONTH A year month interval is made up of a contiguous subset of those fields Keyword Meaning YEAR Years MONTH Months A daytime interval is made up of a contiguous subset of those fields Keyword Meaning DAY Days HOUR Hours MINUTE Minutes SECOND Seconds and possibly fractions of a second The actual subset of fields that comprise a value of either type of interval is defined by an lt interval qualifier gt and this subset is known as the precision of the value Within a value of type interval the first field is constrained only by the lt interval leading field precision gt of the associated lt interval qualifier gt Keyword Valid values of INTERVAL fields YEAR Unconstrained except by lt interval leading field precision gt MONTH Months within years 0 11 DAY Unconstrained except by lt interval leading field precision gt HOUR Hours within days 0 23 MINUTE Minutes within hours 0 59 SECOND Seconds within minutes 0 59 999 Localisation and collations Pyrrho uses the character set names as specified in SQL2011 Specifying a character set restricts the values that can be used not the format of those values By default the UCS character set is used By default the UNICODE collation is used and all collation names supported by the NET framework are supported by
346. value true There are several subclasses of BTree used in the database Some of these implement multilevel indexes BTree itself is a subclass of an abstract class called ATree The BTree class provides the main implementation These basic tree implementations are generic and require a type parameter e g BTree lt long bool gt The supplied type parameters identify the data type used for keys and values BTree is used when the key type is a value type If the key is a class type CTree is used instead In both cases the Key type must implement IComparable The B Tree is a standard fully scalable mechanism for maintaining indexes B Trees as described in textbooks vary in detail so the following account is given here to explain the code A B Tree is formed of nodes called Buckets Each Bucket is either a Leaf bucket or an Inner Bucket A Leaf contains up to N pairs called Slots in the code An Inner Bucket contains Slots whose values are pointers to Buckets and a further pointer to a Bucket so that an Inner Bucket contains pointers to N 1 Buckets altogether at the next level In each Bucket the Slots are kept in order of their key values and the Slots in Inner buckets contain the first key value for the next lower level Bucket so that the extra Bucket is for all values bigger than the last key All of these classes take a type parameter to indicate the key type The value of N in Pyrrho is currently 32 the performance of the databa
347. versions of each for granting or revoking privileges to grantees and for granting or revoking roles to grantees A grantable privilege is a privilege that may be granted by a grant privilege statement it can specify WITH GRANT OPTION in which case the grantee can grant it to others Every database object has an owner This is initially set to the creator of the object and _SYSTEM is considered to have granted the owner all privileges when the object is created On creation a database has a default role with the same name as the database and the owner of the database can use this role to create the starting set of objects for the database The normal way for ownership of a Pyrrho database to be changed is for the database owner to invoke the Pyrrho specific GRANT OWNER statement This is implemented as part of the normal database service and it is good practice to ensure that owners of database objects are user identities that are still available in the operating system 6 4 Roles A role can be created by the CREATE ROLE statement initially the owner has administrative rights on the role granted by SYSTEM The grant role statement is used to allow this role to authorisation idnetifiers and if WITH ADMIN OPTION the grantee may grant it to others Each role is an authorisation identifier SQL recognises a special role called PUBLIC which is associated with any user and is the owner of standard domains In the SQL standard an authorisation
348. which provides a useful critique of a range of commercial DBMS from this viewpoint and supplies a set of interesting exercises to try out on any other supposedly ACID compliant DBMS But rather than merely criticise these products this book offers a set of design proposals for solving the problems of consistency embodied in the open source Pyrrho DBMS In order to show the practicality of these design proposals for advanced database scenarios this book goes beyond simplified examples to showcase Pyrrho s implementation of distributed and partitioned databases and strongly typed features of standard SQL There are some practical sessions in appendices Most of these use Pyrrho as the database engine but the first appendix gives a more general introduction to building database applications using a number of database products Shorter practical exercises are included in the chapters as the corresponding topic is presented Unfortunately no product sticks rigidly to the standard SQL syntax is described in ISO 9075 Pyrrho is closer than most but the SQL syntax appendix is really required reference during practical sessions A final group of appendices cover some technical details on Pyrrho the error codes and system tables 1 Some of these difficulties are caused by transaction properties mandated by the ISO standard for SQL Non compliance with the SQL standard in these areas is legitimate from the viewpoint of this book there are other aspects
349. wing commands on a session restoring the original contents BEGIN TRANSACTION DELETE FROM Accounts INSERT INTO Accounts acctID balance VALUI I S 101 1000 202 2000 ES ES NSERT INTO Accounts acctID balance VALUI ELECT FROM Accounts COMMIT Experiment 3 Simulating Lost update problem 1 client A starts BEGIN TRANSACTION SELECT acctID balance FROM Accounts WHERE acctID 101 2 client B starts BEGIN TRANSACTION SELECT acctID balance FROM Accounts WHERE acctID 101 3 client A continues UPDATE Accounts SET balance 1000 200 WH T RE acctID 101 4 client B continues UPDATE Accounts SET balance 1000 500 WH T RE acctID 101 5 client A continues SELECT acctID balance FROM Accounts WHERE acctID 101 COMMIT 6 client B continues SELECT acctID balance FROM Accounts WHERE acctID 101 COMMIT Note In this experiment we did not have the real Lost Update Problem but after A commits its transaction B usually can proceed and overwrite the update made by A We call this reliability problem as Blind Overwriting or Dirty Write The optimistic concurrency control of Pyrrho solves the Dirty Write Problem Experiment 4 Lost Update Problem fixed by lock
350. y another database and horizontal partitioning where the rows of a table are divided among different databases usually on different servers In this chapter we deal with horizontal partitioning and we will drop the word horizontal for now Partitioned databases are actually a very special case of a connection is to several databases as we will see 10 1 Multiple database connections There are three circumstances in which it is common for a database connection to reference more than one database file These are for partitioned databases master slave database architectures and access to remote data from mobile devices with their own database engine A feature of Pyrrho is the availability of the complete history of the database This means that unless the steps taken in this section are adopted ad hoc tables constructed for data analysis and for other purposes will be persisted in the historical record This is less of a nuisance than might appear for example dropping a table called Fred means that the table name Fred can be used subsequently for a new table names of database objects only need to be currently unique not historically unique Nevertheless if the historical record of the database becomes a source of pride there can be some irritation that users are polluting this history with their ad hoc tables Accordingly Pyrrho has a facility to connect to several databases at once New database objects such as tables created during
351. yle or script If the table s string metadata begins with lt it should be an XSL transform and Pyrrho will generate and then transform the return data as XML 73 The Pyrrho Book May 2015 Chapter 8 Web semantics and OWL According to W3C In addition to the classic Web of documents W3C is helping to build a technology stack to support a Web of data the sort of data you find in databases The term Semantic Web refers to W3C s vision of the Web of linked data Semantic Web technologies enable people to create data stores on the Web build vocabularies and write rules for handling data Linked data are empowered by technologies such as RDF SPARQL OWL and SKOS Anew version of the SPARQL standards was published in 2013 and also RIF RDF and OWL compatibility was one of the early implementers of SPARQL 1 0 and quickly found the non intuitive rules for value equality a real turn off and made querying an RDF database a total nightmare As far as can see the same problems remain and there are so many reasons for values not to be equal that ad hoc queries are always unlikely to yield expected results That said the ambitions of the semantic Web remain exciting e Precise unique URIs can be associated with content items the associations may be direct assigned by someone or inferred For example a web site that hosts a URI might also host a starting set of associations using that URI e The same c
352. your DBMS run by the rules ComputerWorld Oct 21 1985 Crowe M K 2005 Transactions in the Pyrrho Database Engine in Hamza M H ed Proceedings of the IASTED International Conference on Databases and Applications DBA 2005 Innsbruck February 2005 IASTED Anaheim ISBN 0 88986 460 8 ISSN 1027 2666 p 71 76 https www researchgate net publication 220984896 Transactions in the Pyrrho Database Engi ne Crowe M K 2007 An introduction to the source code of the Pyrrho DBMS Computing and Information Systems Technical Reports 40 University of Paisley An updated version is included in the Pyrrho distribution as Sourcelntro docx Curino C Jones E P C Popa R A Malviya N Wu E Madden S Balakrishnan H Zeldovich N 2011 Relational Cloud A Database as a Service for the Cloud 5th Biennial Conference on Innovative Data Systems Research CIDR 2011 January 9 12 2011 Asilomar California Elbushra M M Lindstr m J 2014 Eventual Consistent Databases State of the Art Open Journal of Databases 1 p 26 41 ISSN 2199 3459 http www ronpub com publications OJDB v1i1n03 Elbushra pdf Fernandez E B Washizaki H Yoshioka N VanHilst M 2011 An Approach to Model based Development of Secure and Reliable Systems Availability Reliability and Security ARES 2011 Sixth International Conference on vol no pp 260 265 22 26 Aug 2011 doi 10 1109 ARES 2011 45 Floridi Luciano Sextus Empiricus
353. ype All ll Experimenting with single explicit transactions Autocommit mode CREATE TABLE T id INT NOT NULL PRIMARY KEY s VARCHAR 30 si INTEGER ERT INTO T id s VALUES 1 first SELECT FROM T ROLLBACK what happens Here s another example which I ve left for your amusement It you type exactly what is above Pyrrho does nothing at all SQL gt ROLLBACK what happens H Z un SQL gt _ because there is no transaction active and the PyrrhoCmd program was confused by the strange text If you just say rollback PyrrhoCmd actually tries to say something useful SQL gt ROLLBACK what happens SQL gt ROLLBACK There is no current transaction l actually added the warnings such as There is no current transaction because of this tutorial Even worse was the way that Martti and his students kept pasting in things like Let s try and because this is not correct SQL the transaction would roll back SELECT FROM T Transactional mode testing also use of a DDL command in a transaction BEGIN TRANSACTION CREATE TABLE T2 id INT NOT NULL PRIMARY KEY s VARCHAR 30 INSERT INTO T id s VALUES 2 second INSERT INTO T2 id s VALUES 2 second SELECT FROM T ROLLBACK SELECT FROM T SELECT FROM T2 What has happened to T2
354. yrrho these permissions affect the metadata that can be viewed in a session e g default values view definitions and routine definitions If these are examined by the current user using the system tables the SQL text may contain identifiers that have a different name or are not available to the current user and role Pyrrho displays the identifiers that are appropriate to the current user and role or lt hidden gt if this data is not viewable from the current user and role 6 8 Revoking privileges In the SQL standard it is often a complex matter to discover by what route a particular user is entitled to take a particular action There are many parts of the SQL standard where a schema change results in a cascade of grants of permissions Unfortunately it then becomes very unclear what effect revoking a privilege from a user or role will have as a simple statement of the form revoke all privileges on T from System Fred may allow Fred to retain privileges that he has acquired through some complex chain of grants Some DBMS regard this position as unsatisfactory and in Pyrrho the semantics of grant and revoke operate somewhat differently from the standard The effect is that a revoke statement of the above form will actually leave Fred with no privileges on the specified object and any consequential privileges are also removed in a cascade The derogation from the SQL standard in this respect is extensively documented in the Pyrrho manual
355. yrrhoCmd p 5434 _ Home Share View t H DATA E gt A _ _ 127 0 0 1 5434 974 _ 127 0 0 1 543 _ D osp _ D _ 127 0 0 1 5434 974 _ 127 0 0 1 54 We now start to commit the remote transaction for D2 Enter twice and a Request goes to B which now Saves its transaction information for D2 174 The Pyrrho Book May 2015 EM Command Prompt OSP T p 5434 d A s 0 S 0 M 0 EN Command Prompt OSP T p 5435 d B s 0 S 0 M 0 About to Prepare D2 13 Enter to Continue About to CheckSerialisation D2 13 Enter to Continue e 7 Enter to start EET Enter to Continue 5 Protocol i 4 5 Protocol e Che rialisation Storage Flush complete for A D _ 127 0 0 1 5434 974 _ 127 0 1 54354 1 Protocol 15 Enter to start Protocol byte Requ e D2 13 Enter to Continue rage Flush complete for B D2 _ 0 1 5434 974 127 0 0 1 5435 7 start Home Share View gt insert into E alu into E valu E DATA E gt A 0sp _ _ 127 0 0 1 5434 974 _ 127 0 0 1 _ D osp D _ 127 0 0 1 5434 974 _ 127 0 0 1 54 127 0 Student password true tr 4items j D2 _ 127 0 0 1 543 D2 osp 3 osp Another 2 Enters and A sends the corresponding Request for the other remote transaction the configuration file on B which B also saves EM Command Prompt OSP T Lae d A s 0 S 0 M 0 EM Command Prompt OSP T p 5435 d B s 0 S 0 M 0 Pha

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