Postgresql v14.6 Document Guide

PostgreSQL 14.6 Documentation
The PostgreSQL Global Development Group

The PostgreSQL Global Development Group
Copyright © 1996–2022 The PostgreSQL Global Development Group
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Table of Contents
Preface ................................................................................................................... xxxii
1. What Is PostgreSQL? .................................................................................... xxxii
2. A Brief History of PostgreSQL ....................................................................... xxxii
2.1. The Berkeley POSTGRES Project ........................................................ xxxiii
2.2. Postgres95 ....................................................................................... xxxiii
2.3. PostgreSQL ...................................................................................... xxxiv
3. Conventions ................................................................................................ xxxiv
4. Further Information ...................................................................................... xxxiv
5. Bug Reporting Guidelines .............................................................................. xxxv
5.1. Identifying Bugs ................................................................................ xxxv
5.2. What to Report ................................................................................. xxxvi
5.3. Where to Report Bugs ....................................................................... xxxvii
I. Tutorial .................................................................................................................... 1
1. Getting Started .................................................................................................. 3
1.1. Installation ............................................................................................. 3
1.2. Architectural Fundamentals ....................................................................... 3
1.3. Creating a Database ................................................................................. 3
1.4. Accessing a Database .............................................................................. 5
2. The SQL Language ............................................................................................ 7
2.1. Introduction ............................................................................................ 7
2.2. Concepts ................................................................................................ 7
2.3. Creating a New Table .............................................................................. 7
2.4. Populating a Table With Rows .................................................................. 8
2.5. Querying a Table .................................................................................... 9
2.6. Joins Between Tables ............................................................................. 11
2.7. Aggregate Functions .............................................................................. 13
2.8. Updates ............................................................................................... 14
2.9. Deletions .............................................................................................. 15
3. Advanced Features ........................................................................................... 16
3.1. Introduction .......................................................................................... 16
3.2. Views .................................................................................................. 16
3.3. Foreign Keys ........................................................................................ 16
3.4. Transactions ......................................................................................... 17
3.5. Window Functions ................................................................................. 19
3.6. Inheritance ........................................................................................... 22
3.7. Conclusion ........................................................................................... 23
II. The SQL Language ................................................................................................. 24
4. SQL Syntax .................................................................................................... 32
4.1. Lexical Structure ................................................................................... 32
4.2. Value Expressions ................................................................................. 41
4.3. Calling Functions .................................................................................. 54
5. Data Definition ................................................................................................ 57
5.1. Table Basics ......................................................................................... 57
5.2. Default Values ...................................................................................... 58
5.3. Generated Columns ................................................................................ 59
5.4. Constraints ........................................................................................... 60
5.5. System Columns ................................................................................... 68
5.6. Modifying Tables .................................................................................. 69
5.7. Privileges ............................................................................................. 72
5.8. Row Security Policies ............................................................................ 76
5.9. Schemas ............................................................................................... 82
5.10. Inheritance .......................................................................................... 87
5.11. Table Partitioning ................................................................................ 90
5.12. Foreign Data ..................................................................................... 104
5.13. Other Database Objects ....................................................................... 104
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5.14. Dependency Tracking ......................................................................... 104
6. Data Manipulation .......................................................................................... 107
6.1. Inserting Data ..................................................................................... 107
6.2. Updating Data ..................................................................................... 108
6.3. Deleting Data ...................................................................................... 109
6.4. Returning Data from Modified Rows ....................................................... 109
7. Queries ......................................................................................................... 111
7.1. Overview ............................................................................................ 111
7.2. Table Expressions ................................................................................ 111
7.3. Select Lists ......................................................................................... 127
7.4. Combining Queries (UNION, INTERSECT, EXCEPT) ................................ 129
7.5. Sorting Rows (ORDER BY) .................................................................. 130
7.6. LIMIT and OFFSET ............................................................................ 131
7.7. VALUES Lists ..................................................................................... 131
7.8. WITH Queries (Common Table Expressions) ............................................ 132
8. Data Types .................................................................................................... 142
8.1. Numeric Types .................................................................................... 143
8.2. Monetary Types ................................................................................... 148
8.3. Character Types ................................................................................... 149
8.4. Binary Data Types ............................................................................... 151
8.5. Date/Time Types ................................................................................. 153
8.6. Boolean Type ...................................................................................... 163
8.7. Enumerated Types ............................................................................... 164
8.8. Geometric Types ................................................................................. 165
8.9. Network Address Types ........................................................................ 168
8.10. Bit String Types ................................................................................ 170
8.11. Text Search Types .............................................................................. 171
8.12. UUID Type ....................................................................................... 174
8.13. XML Type ........................................................................................ 174
8.14. JSON Types ...................................................................................... 176
8.15. Arrays .............................................................................................. 187
8.16. Composite Types ............................................................................... 196
8.17. Range Types ..................................................................................... 202
8.18. Domain Types ................................................................................... 209
8.19. Object Identifier Types ....................................................................... 209
8.20. pg_lsn Type ................................................................................... 212
8.21. Pseudo-Types .................................................................................... 212
9. Functions and Operators .................................................................................. 214
9.1. Logical Operators ................................................................................ 214
9.2. Comparison Functions and Operators ...................................................... 215
9.3. Mathematical Functions and Operators .................................................... 219
9.4. String Functions and Operators .............................................................. 226
9.5. Binary String Functions and Operators .................................................... 235
9.6. Bit String Functions and Operators ......................................................... 239
9.7. Pattern Matching ................................................................................. 241
9.8. Data Type Formatting Functions ............................................................. 258
9.9. Date/Time Functions and Operators ........................................................ 266
9.10. Enum Support Functions ..................................................................... 282
9.11. Geometric Functions and Operators ....................................................... 283
9.12. Network Address Functions and Operators .............................................. 290
9.13. Text Search Functions and Operators ..................................................... 293
9.14. UUID Functions ................................................................................ 299
9.15. XML Functions ................................................................................. 299
9.16. JSON Functions and Operators ............................................................. 314
9.17. Sequence Manipulation Functions ......................................................... 332
9.18. Conditional Expressions ...................................................................... 333
9.19. Array Functions and Operators ............................................................. 336
9.20. Range/Multirange Functions and Operators ............................................. 340
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9.21. Aggregate Functions ........................................................................... 345
9.22. Window Functions ............................................................................. 352
9.23. Subquery Expressions ......................................................................... 354
9.24. Row and Array Comparisons ............................................................... 356
9.25. Set Returning Functions ...................................................................... 359
9.26. System Information Functions and Operators .......................................... 362
9.27. System Administration Functions .......................................................... 379
9.28. Trigger Functions ............................................................................... 395
9.29. Event Trigger Functions ...................................................................... 396
9.30. Statistics Information Functions ............................................................ 399
10. Type Conversion .......................................................................................... 401
10.1. Overview .......................................................................................... 401
10.2. Operators .......................................................................................... 402
10.3. Functions .......................................................................................... 406
10.4. Value Storage .................................................................................... 410
10.5. UNION, CASE, and Related Constructs .................................................. 411
10.6. SELECT Output Columns .................................................................... 412
11. Indexes ....................................................................................................... 414
11.1. Introduction ....................................................................................... 414
11.2. Index Types ...................................................................................... 415
11.3. Multicolumn Indexes .......................................................................... 417
11.4. Indexes and ORDER BY ..................................................................... 418
11.5. Combining Multiple Indexes ................................................................ 419
11.6. Unique Indexes .................................................................................. 419
11.7. Indexes on Expressions ....................................................................... 420
11.8. Partial Indexes ................................................................................... 420
11.9. Index-Only Scans and Covering Indexes ................................................ 423
11.10. Operator Classes and Operator Families ................................................ 426
11.11. Indexes and Collations ...................................................................... 427
11.12. Examining Index Usage ..................................................................... 428
12. Full Text Search ........................................................................................... 430
12.1. Introduction ....................................................................................... 430
12.2. Tables and Indexes ............................................................................. 434
12.3. Controlling Text Search ...................................................................... 436
12.4. Additional Features ............................................................................ 443
12.5. Parsers ............................................................................................. 449
12.6. Dictionaries ....................................................................................... 450
12.7. Configuration Example ....................................................................... 460
12.8. Testing and Debugging Text Search ...................................................... 461
12.9. Preferred Index Types for Text Search ................................................... 466
12.10. psql Support .................................................................................... 467
12.11. Limitations ...................................................................................... 470
13. Concurrency Control ..................................................................................... 471
13.1. Introduction ....................................................................................... 471
13.2. Transaction Isolation ........................................................................... 471
13.3. Explicit Locking ................................................................................ 477
13.4. Data Consistency Checks at the Application Level ................................... 482
13.5. Caveats ............................................................................................. 484
13.6. Locking and Indexes ........................................................................... 484
14. Performance Tips ......................................................................................... 486
14.1. Using EXPLAIN ................................................................................ 486
14.2. Statistics Used by the Planner .............................................................. 498
14.3. Controlling the Planner with Explicit JOIN Clauses ................................. 503
14.4. Populating a Database ......................................................................... 505
14.5. Non-Durable Settings .......................................................................... 508
15. Parallel Query .............................................................................................. 509
15.1. How Parallel Query Works .................................................................. 509
15.2. When Can Parallel Query Be Used? ...................................................... 510
v

15.3. Parallel Plans ..................................................................................... 511
15.4. Parallel Safety ................................................................................... 513
III. Server Administration ............................................................................................ 515
16. Installation from Binaries ............................................................................... 522
17. Installation from Source Code ......................................................................... 523
17.1. Short Version .................................................................................... 523
17.2. Requirements ..................................................................................... 523
17.3. Getting the Source .............................................................................. 525
17.4. Installation Procedure .......................................................................... 525
17.5. Post-Installation Setup ......................................................................... 538
17.6. Supported Platforms ........................................................................... 539
17.7. Platform-Specific Notes ....................................................................... 539
18. Installation from Source Code on Windows ....................................................... 545
18.1. Building with Visual C++ or the Microsoft Windows SDK ........................ 545
19. Server Setup and Operation ............................................................................ 551
19.1. The PostgreSQL User Account ............................................................. 551
19.2. Creating a Database Cluster ................................................................. 551
19.3. Starting the Database Server ................................................................ 553
19.4. Managing Kernel Resources ................................................................. 557
19.5. Shutting Down the Server .................................................................... 565
19.6. Upgrading a PostgreSQL Cluster .......................................................... 566
19.7. Preventing Server Spoofing .................................................................. 568
19.8. Encryption Options ............................................................................. 569
19.9. Secure TCP/IP Connections with SSL .................................................... 570
19.10. Secure TCP/IP Connections with GSSAPI Encryption ............................. 574
19.11. Secure TCP/IP Connections with SSH Tunnels ...................................... 574
19.12. Registering Event Log on Windows ..................................................... 575
20. Server Configuration ..................................................................................... 577
20.1. Setting Parameters .............................................................................. 577
20.2. File Locations .................................................................................... 581
20.3. Connections and Authentication ............................................................ 582
20.4. Resource Consumption ........................................................................ 588
20.5. Write Ahead Log ............................................................................... 597
20.6. Replication ........................................................................................ 606
20.7. Query Planning .................................................................................. 613
20.8. Error Reporting and Logging ............................................................... 619
20.9. Run-time Statistics ............................................................................. 632
20.10. Automatic Vacuuming ....................................................................... 633
20.11. Client Connection Defaults ................................................................. 635
20.12. Lock Management ............................................................................ 645
20.13. Version and Platform Compatibility ..................................................... 646
20.14. Error Handling ................................................................................. 648
20.15. Preset Options .................................................................................. 648
20.16. Customized Options .......................................................................... 650
20.17. Developer Options ............................................................................ 650
20.18. Short Options ................................................................................... 655
21. Client Authentication ..................................................................................... 657
21.1. The pg_hba.conf File ..................................................................... 657
21.2. User Name Maps ............................................................................... 665
21.3. Authentication Methods ....................................................................... 667
21.4. Trust Authentication ........................................................................... 667
21.5. Password Authentication ..................................................................... 668
21.6. GSSAPI Authentication ....................................................................... 669
21.7. SSPI Authentication ............................................................................ 670
21.8. Ident Authentication ........................................................................... 671
21.9. Peer Authentication ............................................................................ 672
21.10. LDAP Authentication ........................................................................ 672
21.11. RADIUS Authentication .................................................................... 675
vi

21.12. Certificate Authentication ................................................................... 676
21.13. PAM Authentication ......................................................................... 676
21.14. BSD Authentication .......................................................................... 677
21.15. Authentication Problems .................................................................... 677
22. Database Roles ............................................................................................. 679
22.1. Database Roles .................................................................................. 679
22.2. Role Attributes .................................................................................. 680
22.3. Role Membership ............................................................................... 681
22.4. Dropping Roles .................................................................................. 683
22.5. Predefined Roles ................................................................................ 683
22.6. Function Security ............................................................................... 685
23. Managing Databases ..................................................................................... 686
23.1. Overview .......................................................................................... 686
23.2. Creating a Database ............................................................................ 686
23.3. Template Databases ............................................................................ 687
23.4. Database Configuration ....................................................................... 688
23.5. Destroying a Database ........................................................................ 689
23.6. Tablespaces ....................................................................................... 689
24. Localization ................................................................................................. 692
24.1. Locale Support .................................................................................. 692
24.2. Collation Support ............................................................................... 694
24.3. Character Set Support ......................................................................... 700
25. Routine Database Maintenance Tasks ............................................................... 711
25.1. Routine Vacuuming ............................................................................ 711
25.2. Routine Reindexing ............................................................................ 719
25.3. Log File Maintenance ......................................................................... 719
26. Backup and Restore ...................................................................................... 722
26.1. SQL Dump ....................................................................................... 722
26.2. File System Level Backup ................................................................... 725
26.3. Continuous Archiving and Point-in-Time Recovery (PITR) ........................ 726
27. High Availability, Load Balancing, and Replication ............................................ 738
27.1. Comparison of Different Solutions ........................................................ 738
27.2. Log-Shipping Standby Servers .............................................................. 741
27.3. Failover ............................................................................................ 750
27.4. Hot Standby ...................................................................................... 751
28. Monitoring Database Activity ......................................................................... 759
28.1. Standard Unix Tools ........................................................................... 759
28.2. The Statistics Collector ....................................................................... 760
28.3. Viewing Locks .................................................................................. 794
28.4. Progress Reporting ............................................................................. 794
28.5. Dynamic Tracing ............................................................................... 802
29. Monitoring Disk Usage .................................................................................. 811
29.1. Determining Disk Usage ..................................................................... 811
29.2. Disk Full Failure ................................................................................ 812
30. Reliability and the Write-Ahead Log ................................................................ 813
30.1. Reliability ......................................................................................... 813
30.2. Data Checksums ................................................................................ 815
30.3. Write-Ahead Logging (WAL) ............................................................... 815
30.4. Asynchronous Commit ........................................................................ 816
30.5. WAL Configuration ............................................................................ 817
30.6. WAL Internals ................................................................................... 820
31. Logical Replication ....................................................................................... 822
31.1. Publication ........................................................................................ 822
31.2. Subscription ...................................................................................... 823
31.3. Conflicts ........................................................................................... 824
31.4. Restrictions ....................................................................................... 824
31.5. Architecture ...................................................................................... 825
31.6. Monitoring ........................................................................................ 826
vii

31.7. Security ............................................................................................ 826
31.8. Configuration Settings ......................................................................... 826
31.9. Quick Setup ...................................................................................... 827
32. Just-in-Time Compilation (JIT) ....................................................................... 828
32.1. What Is JIT compilation? .................................................................... 828
32.2. When to JIT? .................................................................................... 828
32.3. Configuration .................................................................................... 830
32.4. Extensibility ...................................................................................... 830
33. Regression Tests ........................................................................................... 831
33.1. Running the Tests .............................................................................. 831
33.2. Test Evaluation .................................................................................. 835
33.3. Variant Comparison Files .................................................................... 837
33.4. TAP Tests ......................................................................................... 838
33.5. Test Coverage Examination ................................................................. 839
IV. Client Interfaces ................................................................................................... 840
34. libpq — C Library ........................................................................................ 845
34.1. Database Connection Control Functions ................................................. 845
34.2. Connection Status Functions ................................................................ 861
34.3. Command Execution Functions ............................................................. 867
34.4. Asynchronous Command Processing ...................................................... 883
34.5. Pipeline Mode ................................................................................... 887
34.6. Retrieving Query Results Row-by-Row .................................................. 891
34.7. Canceling Queries in Progress .............................................................. 892
34.8. The Fast-Path Interface ....................................................................... 893
34.9. Asynchronous Notification ................................................................... 894
34.10. Functions Associated with the COPY Command ..................................... 895
34.11. Control Functions ............................................................................. 899
34.12. Miscellaneous Functions .................................................................... 901
34.13. Notice Processing ............................................................................. 905
34.14. Event System ................................................................................... 906
34.15. Environment Variables ...................................................................... 912
34.16. The Password File ............................................................................ 914
34.17. The Connection Service File ............................................................... 914
34.18. LDAP Lookup of Connection Parameters .............................................. 915
34.19. SSL Support .................................................................................... 916
34.20. Behavior in Threaded Programs .......................................................... 920
34.21. Building libpq Programs .................................................................... 921
34.22. Example Programs ............................................................................ 922
35. Large Objects .............................................................................................. 933
35.1. Introduction ....................................................................................... 933
35.2. Implementation Features ...................................................................... 933
35.3. Client Interfaces ................................................................................. 933
35.4. Server-Side Functions ......................................................................... 938
35.5. Example Program ............................................................................... 939
36. ECPG — Embedded SQL in C ....................................................................... 945
36.1. The Concept ...................................................................................... 945
36.2. Managing Database Connections ........................................................... 945
36.3. Running SQL Commands .................................................................... 949
36.4. Using Host Variables .......................................................................... 952
36.5. Dynamic SQL ................................................................................... 966
36.6. pgtypes Library .................................................................................. 968
36.7. Using Descriptor Areas ....................................................................... 982
36.8. Error Handling ................................................................................... 995
36.9. Preprocessor Directives ..................................................................... 1002
36.10. Processing Embedded SQL Programs ................................................. 1004
36.11. Library Functions ............................................................................ 1005
36.12. Large Objects ................................................................................. 1006
36.13. C++ Applications ............................................................................ 1007
viii

36.14. Embedded SQL Commands .............................................................. 1011
36.15. Informix Compatibility Mode ............................................................ 1036
36.16. Oracle Compatibility Mode ............................................................... 1051
36.17. Internals ........................................................................................ 1051
37. The Information Schema .............................................................................. 1054
37.1. The Schema ..................................................................................... 1054
37.2. Data Types ...................................................................................... 1054
37.3. information_schema_catalog_name ........................................ 1055
37.4. administrable_role_authorizations .................................... 1055
37.5. applicable_roles ..................................................................... 1055
37.6. attributes ................................................................................. 1056
37.7. character_sets ......................................................................... 1058
37.8. check_constraint_routine_usage .......................................... 1059
37.9. check_constraints ................................................................... 1059
37.10. collations ................................................................................ 1060
37.11. collation_character_set_applicability .......................... 1060
37.12. column_column_usage .............................................................. 1061
37.13. column_domain_usage .............................................................. 1061
37.14. column_options ........................................................................ 1061
37.15. column_privileges .................................................................. 1062
37.16. column_udt_usage .................................................................... 1063
37.17. columns ...................................................................................... 1063
37.18. constraint_column_usage ...................................................... 1066
37.19. constraint_table_usage ........................................................ 1067
37.20. data_type_privileges ............................................................ 1067
37.21. domain_constraints ................................................................ 1068
37.22. domain_udt_usage .................................................................... 1068
37.23. domains ...................................................................................... 1069
37.24. element_types .......................................................................... 1071
37.25. enabled_roles .......................................................................... 1073
37.26. foreign_data_wrapper_options ............................................ 1073
37.27. foreign_data_wrappers .......................................................... 1074
37.28. foreign_server_options ........................................................ 1074
37.29. foreign_servers ...................................................................... 1074
37.30. foreign_table_options .......................................................... 1075
37.31. foreign_tables ........................................................................ 1075
37.32. key_column_usage .................................................................... 1076
37.33. parameters ................................................................................ 1076
37.34. referential_constraints ...................................................... 1078
37.35. role_column_grants ................................................................ 1079
37.36. role_routine_grants .............................................................. 1079
37.37. role_table_grants .................................................................. 1080
37.38. role_udt_grants ...................................................................... 1081
37.39. role_usage_grants .................................................................. 1081
37.40. routine_column_usage ............................................................ 1082
37.41. routine_privileges ................................................................ 1082
37.42. routine_routine_usage .......................................................... 1083
37.43. routine_sequence_usage ........................................................ 1084
37.44. routine_table_usage .............................................................. 1084
37.45. routines .................................................................................... 1085
37.46. schemata .................................................................................... 1089
37.47. sequences .................................................................................. 1089
37.48. sql_features ............................................................................ 1090
37.49. sql_implementation_info ...................................................... 1091
37.50. sql_parts .................................................................................. 1091
37.51. sql_sizing ................................................................................ 1092
37.52. table_constraints .................................................................. 1092
37.53. table_privileges .................................................................... 1093
ix

37.54. tables ........................................................................................ 1093
37.55. transforms ................................................................................ 1094
37.56. triggered_update_columns .................................................... 1095
37.57. triggers .................................................................................... 1095
37.58. udt_privileges ........................................................................ 1097
37.59. usage_privileges .................................................................... 1097
37.60. user_defined_types ................................................................ 1098
37.61. user_mapping_options ............................................................ 1100
37.62. user_mappings .......................................................................... 1100
37.63. view_column_usage .................................................................. 1100
37.64. view_routine_usage ................................................................ 1101
37.65. view_table_usage .................................................................... 1101
37.66. views .......................................................................................... 1102
V. Server Programming ............................................................................................. 1104
38. Extending SQL ........................................................................................... 1110
38.1. How Extensibility Works ................................................................... 1110
38.2. The PostgreSQL Type System ............................................................ 1110
38.3. User-Defined Functions ..................................................................... 1113
38.4. User-Defined Procedures ................................................................... 1114
38.5. Query Language (SQL) Functions ....................................................... 1114
38.6. Function Overloading ........................................................................ 1131
38.7. Function Volatility Categories ............................................................. 1132
38.8. Procedural Language Functions ........................................................... 1134
38.9. Internal Functions ............................................................................. 1134
38.10. C-Language Functions ..................................................................... 1134
38.11. Function Optimization Information .................................................... 1155
38.12. User-Defined Aggregates ................................................................. 1156
38.13. User-Defined Types ........................................................................ 1163
38.14. User-Defined Operators ................................................................... 1168
38.15. Operator Optimization Information .................................................... 1168
38.16. Interfacing Extensions to Indexes ....................................................... 1172
38.17. Packaging Related Objects into an Extension ....................................... 1185
38.18. Extension Building Infrastructure ....................................................... 1194
39. Triggers ..................................................................................................... 1198
39.1. Overview of Trigger Behavior ............................................................ 1198
39.2. Visibility of Data Changes ................................................................. 1201
39.3. Writing Trigger Functions in C ........................................................... 1201
39.4. A Complete Trigger Example ............................................................. 1204
40. Event Triggers ............................................................................................ 1208
40.1. Overview of Event Trigger Behavior .................................................... 1208
40.2. Event Trigger Firing Matrix ............................................................... 1209
40.3. Writing Event Trigger Functions in C .................................................. 1212
40.4. A Complete Event Trigger Example .................................................... 1213
40.5. A Table Rewrite Event Trigger Example .............................................. 1214
41. The Rule System ........................................................................................ 1216
41.1. The Query Tree ................................................................................ 1216
41.2. Views and the Rule System ................................................................ 1217
41.3. Materialized Views ........................................................................... 1224
41.4. Rules on INSERT, UPDATE, and DELETE ........................................... 1227
41.5. Rules and Privileges .......................................................................... 1238
41.6. Rules and Command Status ................................................................ 1240
41.7. Rules Versus Triggers ....................................................................... 1240
42. Procedural Languages .................................................................................. 1243
42.1. Installing Procedural Languages .......................................................... 1243
43. PL/pgSQL — SQL Procedural Language ........................................................ 1246
43.1. Overview ........................................................................................ 1246
43.2. Structure of PL/pgSQL ...................................................................... 1247
43.3. Declarations ..................................................................................... 1249
x

43.4. Expressions ..................................................................................... 1255
43.5. Basic Statements .............................................................................. 1256
43.6. Control Structures ............................................................................. 1264
43.7. Cursors ........................................................................................... 1279
43.8. Transaction Management ................................................................... 1285
43.9. Errors and Messages ......................................................................... 1286
43.10. Trigger Functions ............................................................................ 1288
43.11. PL/pgSQL under the Hood ............................................................... 1297
43.12. Tips for Developing in PL/pgSQL ..................................................... 1300
43.13. Porting from Oracle PL/SQL ............................................................ 1304
44. PL/Tcl — Tcl Procedural Language ............................................................... 1314
44.1. Overview ........................................................................................ 1314
44.2. PL/Tcl Functions and Arguments ........................................................ 1314
44.3. Data Values in PL/Tcl ....................................................................... 1316
44.4. Global Data in PL/Tcl ....................................................................... 1316
44.5. Database Access from PL/Tcl ............................................................. 1317
44.6. Trigger Functions in PL/Tcl ............................................................... 1319
44.7. Event Trigger Functions in PL/Tcl ....................................................... 1321
44.8. Error Handling in PL/Tcl ................................................................... 1321
44.9. Explicit Subtransactions in PL/Tcl ....................................................... 1322
44.10. Transaction Management .................................................................. 1323
44.11. PL/Tcl Configuration ....................................................................... 1324
44.12. Tcl Procedure Names ...................................................................... 1324
45. PL/Perl — Perl Procedural Language ............................................................. 1325
45.1. PL/Perl Functions and Arguments ....................................................... 1325
45.2. Data Values in PL/Perl ...................................................................... 1330
45.3. Built-in Functions ............................................................................. 1330
45.4. Global Values in PL/Perl ................................................................... 1335
45.5. Trusted and Untrusted PL/Perl ............................................................ 1336
45.6. PL/Perl Triggers ............................................................................... 1337
45.7. PL/Perl Event Triggers ...................................................................... 1338
45.8. PL/Perl Under the Hood .................................................................... 1339
46. PL/Python — Python Procedural Language ..................................................... 1341
46.1. Python 2 vs. Python 3 ....................................................................... 1341
46.2. PL/Python Functions ......................................................................... 1342
46.3. Data Values ..................................................................................... 1343
46.4. Sharing Data .................................................................................... 1349
46.5. Anonymous Code Blocks ................................................................... 1349
46.6. Trigger Functions ............................................................................. 1349
46.7. Database Access ............................................................................... 1350
46.8. Explicit Subtransactions ..................................................................... 1354
46.10. Utility Functions ............................................................................. 1356
46.11. Environment Variables ..................................................................... 1357
47. Server Programming Interface ....................................................................... 1358
47.1. Interface Functions ........................................................................... 1358
47.2. Interface Support Functions ................................................................ 1400
47.3. Memory Management ....................................................................... 1409
47.5. Visibility of Data Changes ................................................................. 1422
47.6. Examples ........................................................................................ 1422
48. Background Worker Processes ...................................................................... 1426
49. Logical Decoding ........................................................................................ 1429
49.1. Logical Decoding Examples ............................................................... 1429
49.2. Logical Decoding Concepts ................................................................ 1432
49.3. Streaming Replication Protocol Interface .............................................. 1434
49.4. Logical Decoding SQL Interface ......................................................... 1434
49.5. System Catalogs Related to Logical Decoding ....................................... 1434
xi

49.6. Logical Decoding Output Plugins ........................................................ 1434
49.7. Logical Decoding Output Writers ........................................................ 1442
49.8. Synchronous Replication Support for Logical Decoding ........................... 1442
49.9. Streaming of Large Transactions for Logical Decoding ............................ 1443
49.10. Two-phase Commit Support for Logical Decoding ................................ 1444
50. Replication Progress Tracking ....................................................................... 1446
VI. Reference .......................................................................................................... 1447
I. SQL Commands ............................................................................................ 1452
ABORT .................................................................................................. 1456
ALTER AGGREGATE ............................................................................. 1457
ALTER COLLATION .............................................................................. 1459
ALTER CONVERSION ............................................................................ 1462
ALTER DATABASE ................................................................................ 1464
ALTER DEFAULT PRIVILEGES .............................................................. 1467
ALTER DOMAIN .................................................................................... 1470
ALTER EVENT TRIGGER ....................................................................... 1474
ALTER EXTENSION ............................................................................... 1475
ALTER FOREIGN DATA WRAPPER ........................................................ 1479
ALTER FOREIGN TABLE ....................................................................... 1481
ALTER FUNCTION ................................................................................. 1486
ALTER GROUP ...................................................................................... 1490
ALTER INDEX ....................................................................................... 1492
ALTER LANGUAGE ............................................................................... 1495
ALTER LARGE OBJECT ......................................................................... 1496
ALTER MATERIALIZED VIEW ............................................................... 1497
ALTER OPERATOR ................................................................................ 1499
ALTER OPERATOR CLASS .................................................................... 1501
ALTER OPERATOR FAMILY .................................................................. 1502
ALTER POLICY ..................................................................................... 1506
ALTER PROCEDURE .............................................................................. 1508
ALTER PUBLICATION ........................................................................... 1511
ALTER ROLE ......................................................................................... 1513
ALTER ROUTINE ................................................................................... 1517
ALTER RULE ......................................................................................... 1519
ALTER SCHEMA ................................................................................... 1520
ALTER SEQUENCE ................................................................................ 1521
ALTER SERVER ..................................................................................... 1524
ALTER STATISTICS ............................................................................... 1526
ALTER SUBSCRIPTION .......................................................................... 1527
ALTER SYSTEM .................................................................................... 1530
ALTER TABLE ....................................................................................... 1532
ALTER TABLESPACE ............................................................................ 1549
ALTER TEXT SEARCH CONFIGURATION .............................................. 1551
ALTER TEXT SEARCH DICTIONARY ..................................................... 1553
ALTER TEXT SEARCH PARSER ............................................................. 1555
ALTER TEXT SEARCH TEMPLATE ........................................................ 1556
ALTER TRIGGER ................................................................................... 1557
ALTER TYPE ......................................................................................... 1559
ALTER USER ......................................................................................... 1564
ALTER USER MAPPING ......................................................................... 1565
ALTER VIEW ......................................................................................... 1566
ANALYZE .............................................................................................. 1568
BEGIN ................................................................................................... 1571
CALL ..................................................................................................... 1573
CHECKPOINT ........................................................................................ 1575
CLOSE ................................................................................................... 1576
CLUSTER .............................................................................................. 1577
COMMENT ............................................................................................ 1580
xii

COMMIT ................................................................................................ 1585
COMMIT PREPARED ............................................................................. 1586
COPY .................................................................................................... 1587
CREATE ACCESS METHOD ................................................................... 1597
CREATE AGGREGATE ........................................................................... 1598
CREATE CAST ....................................................................................... 1606
CREATE COLLATION ............................................................................ 1610
CREATE CONVERSION .......................................................................... 1613
CREATE DATABASE ............................................................................. 1615
CREATE DOMAIN ................................................................................. 1619
CREATE EVENT TRIGGER ..................................................................... 1622
CREATE EXTENSION ............................................................................ 1624
CREATE FOREIGN DATA WRAPPER ...................................................... 1627
CREATE FOREIGN TABLE ..................................................................... 1629
CREATE FUNCTION .............................................................................. 1634
CREATE GROUP .................................................................................... 1643
CREATE INDEX ..................................................................................... 1644
CREATE LANGUAGE ............................................................................. 1653
CREATE MATERIALIZED VIEW ............................................................. 1656
CREATE OPERATOR .............................................................................. 1658
CREATE OPERATOR CLASS .................................................................. 1661
CREATE OPERATOR FAMILY ................................................................ 1664
CREATE POLICY ................................................................................... 1665
CREATE PROCEDURE ........................................................................... 1671
CREATE PUBLICATION ......................................................................... 1675
CREATE ROLE ...................................................................................... 1678
CREATE RULE ...................................................................................... 1683
CREATE SCHEMA ................................................................................. 1686
CREATE SEQUENCE .............................................................................. 1689
CREATE SERVER .................................................................................. 1693
CREATE STATISTICS ............................................................................. 1695
CREATE SUBSCRIPTION ....................................................................... 1699
CREATE TABLE .................................................................................... 1702
CREATE TABLE AS ............................................................................... 1724
CREATE TABLESPACE .......................................................................... 1727
CREATE TEXT SEARCH CONFIGURATION ............................................ 1729
CREATE TEXT SEARCH DICTIONARY ................................................... 1730
CREATE TEXT SEARCH PARSER ........................................................... 1732
CREATE TEXT SEARCH TEMPLATE ...................................................... 1734
CREATE TRANSFORM ........................................................................... 1735
CREATE TRIGGER ................................................................................. 1737
CREATE TYPE ....................................................................................... 1744
CREATE USER ....................................................................................... 1753
CREATE USER MAPPING ....................................................................... 1754
CREATE VIEW ...................................................................................... 1756
DEALLOCATE ....................................................................................... 1761
DECLARE .............................................................................................. 1762
DELETE ................................................................................................. 1766
DISCARD ............................................................................................... 1769
DO ........................................................................................................ 1770
DROP ACCESS METHOD ....................................................................... 1772
DROP AGGREGATE ............................................................................... 1773
DROP CAST ........................................................................................... 1775
DROP COLLATION ................................................................................ 1776
DROP CONVERSION .............................................................................. 1777
DROP DATABASE ................................................................................. 1778
DROP DOMAIN ...................................................................................... 1779
DROP EVENT TRIGGER ......................................................................... 1780
xiii

DROP EXTENSION ................................................................................. 1781
DROP FOREIGN DATA WRAPPER .......................................................... 1782
DROP FOREIGN TABLE ......................................................................... 1783
DROP FUNCTION .................................................................................. 1784
DROP GROUP ........................................................................................ 1786
DROP INDEX ......................................................................................... 1787
DROP LANGUAGE ................................................................................. 1789
DROP MATERIALIZED VIEW ................................................................. 1790
DROP OPERATOR .................................................................................. 1791
DROP OPERATOR CLASS ...................................................................... 1793
DROP OPERATOR FAMILY .................................................................... 1795
DROP OWNED ....................................................................................... 1797
DROP POLICY ....................................................................................... 1798
DROP PROCEDURE ............................................................................... 1799
DROP PUBLICATION ............................................................................. 1801
DROP ROLE .......................................................................................... 1802
DROP ROUTINE ..................................................................................... 1803
DROP RULE .......................................................................................... 1805
DROP SCHEMA ..................................................................................... 1806
DROP SEQUENCE .................................................................................. 1807
DROP SERVER ...................................................................................... 1808
DROP STATISTICS ................................................................................. 1809
DROP SUBSCRIPTION ............................................................................ 1810
DROP TABLE ........................................................................................ 1812
DROP TABLESPACE .............................................................................. 1813
DROP TEXT SEARCH CONFIGURATION ................................................ 1814
DROP TEXT SEARCH DICTIONARY ....................................................... 1815
DROP TEXT SEARCH PARSER ............................................................... 1816
DROP TEXT SEARCH TEMPLATE .......................................................... 1817
DROP TRANSFORM ............................................................................... 1818
DROP TRIGGER ..................................................................................... 1819
DROP TYPE ........................................................................................... 1820
DROP USER ........................................................................................... 1821
DROP USER MAPPING ........................................................................... 1822
DROP VIEW .......................................................................................... 1823
END ...................................................................................................... 1824
EXECUTE .............................................................................................. 1825
EXPLAIN ............................................................................................... 1826
FETCH ................................................................................................... 1831
GRANT .................................................................................................. 1835
IMPORT FOREIGN SCHEMA .................................................................. 1840
INSERT .................................................................................................. 1842
LISTEN .................................................................................................. 1850
LOAD .................................................................................................... 1852
LOCK .................................................................................................... 1853
MOVE ................................................................................................... 1856
NOTIFY ................................................................................................. 1858
PREPARE ............................................................................................... 1861
PREPARE TRANSACTION ...................................................................... 1864
REASSIGN OWNED ............................................................................... 1866
REFRESH MATERIALIZED VIEW ........................................................... 1867
REINDEX ............................................................................................... 1869
RELEASE SAVEPOINT ........................................................................... 1874
RESET ................................................................................................... 1876
REVOKE ................................................................................................ 1877
ROLLBACK ........................................................................................... 1881
ROLLBACK PREPARED ......................................................................... 1882
ROLLBACK TO SAVEPOINT .................................................................. 1883
xiv

SAVEPOINT ........................................................................................... 1885
SECURITY LABEL ................................................................................. 1887
SELECT ................................................................................................. 1890
SELECT INTO ........................................................................................ 1912
SET ....................................................................................................... 1914
SET CONSTRAINTS ............................................................................... 1917
SET ROLE ............................................................................................. 1918
SET SESSION AUTHORIZATION ............................................................ 1920
SET TRANSACTION ............................................................................... 1922
SHOW ................................................................................................... 1925
START TRANSACTION .......................................................................... 1927
TRUNCATE ........................................................................................... 1928
UNLISTEN ............................................................................................. 1930
UPDATE ................................................................................................ 1932
VACUUM .............................................................................................. 1937
VALUES ................................................................................................ 1941
II. PostgreSQL Client Applications ..................................................................... 1944
clusterdb ................................................................................................. 1945
createdb .................................................................................................. 1948
createuser ................................................................................................ 1951
dropdb .................................................................................................... 1955
dropuser .................................................................................................. 1958
ecpg ....................................................................................................... 1961
pg_amcheck ............................................................................................ 1964
pg_basebackup ......................................................................................... 1970
pgbench .................................................................................................. 1978
pg_config ................................................................................................ 1998
pg_dump ................................................................................................. 2001
pg_dumpall ............................................................................................. 2014
pg_isready ............................................................................................... 2021
pg_receivewal .......................................................................................... 2023
pg_recvlogical ......................................................................................... 2027
pg_restore ............................................................................................... 2031
pg_verifybackup ....................................................................................... 2040
psql ........................................................................................................ 2043
reindexdb ................................................................................................ 2085
vacuumdb ............................................................................................... 2089
III. PostgreSQL Server Applications .................................................................... 2095
initdb ..................................................................................................... 2096
pg_archivecleanup .................................................................................... 2101
pg_checksums .......................................................................................... 2103
pg_controldata ......................................................................................... 2105
pg_ctl ..................................................................................................... 2106
pg_resetwal ............................................................................................. 2112
pg_rewind ............................................................................................... 2116
pg_test_fsync ........................................................................................... 2120
pg_test_timing ......................................................................................... 2121
pg_upgrade .............................................................................................. 2125
pg_waldump ............................................................................................ 2133
postgres .................................................................................................. 2136
postmaster ............................................................................................... 2143
VII. Internals ........................................................................................................... 2144
51. Overview of PostgreSQL Internals ................................................................. 2150
51.1. The Path of a Query ......................................................................... 2150
51.2. How Connections Are Established ....................................................... 2150
51.3. The Parser Stage .............................................................................. 2151
51.4. The PostgreSQL Rule System ............................................................. 2152
51.5. Planner/Optimizer ............................................................................. 2152
xv

51.6. Executor ......................................................................................... 2153
52. System Catalogs ......................................................................................... 2155
52.1. Overview ........................................................................................ 2155
52.2. pg_aggregate ............................................................................. 2157
52.3. pg_am ........................................................................................... 2158
52.4. pg_amop ....................................................................................... 2159
52.5. pg_amproc ................................................................................... 2160
52.6. pg_attrdef ................................................................................. 2160
52.7. pg_attribute ............................................................................. 2160
52.8. pg_authid ................................................................................... 2162
52.9. pg_auth_members ....................................................................... 2164
52.10. pg_cast ...................................................................................... 2164
52.11. pg_class .................................................................................... 2165
52.12. pg_collation ............................................................................ 2167
52.13. pg_constraint .......................................................................... 2168
52.14. pg_conversion .......................................................................... 2170
52.15. pg_database .............................................................................. 2170
52.16. pg_db_role_setting ................................................................ 2171
52.17. pg_default_acl ........................................................................ 2172
52.18. pg_depend .................................................................................. 2172
52.19. pg_description ........................................................................ 2174
52.20. pg_enum ...................................................................................... 2175
52.21. pg_event_trigger .................................................................... 2175
52.22. pg_extension ............................................................................ 2176
52.23. pg_foreign_data_wrapper ...................................................... 2176
52.24. pg_foreign_server .................................................................. 2177
52.25. pg_foreign_table .................................................................... 2177
52.26. pg_index .................................................................................... 2178
52.27. pg_inherits .............................................................................. 2179
52.28. pg_init_privs .......................................................................... 2180
52.29. pg_language .............................................................................. 2180
52.30. pg_largeobject ........................................................................ 2181
52.31. pg_largeobject_metadata ...................................................... 2181
52.32. pg_namespace ............................................................................ 2182
52.33. pg_opclass ................................................................................ 2182
52.34. pg_operator .............................................................................. 2183
52.35. pg_opfamily .............................................................................. 2184
52.36. pg_partitioned_table ............................................................ 2184
52.37. pg_policy .................................................................................. 2185
52.38. pg_proc ...................................................................................... 2186
52.39. pg_publication ........................................................................ 2188
52.40. pg_publication_rel ................................................................ 2189
52.41. pg_range .................................................................................... 2189
52.42. pg_replication_origin .......................................................... 2189
52.43. pg_rewrite ................................................................................ 2190
52.44. pg_seclabel .............................................................................. 2190
52.45. pg_sequence .............................................................................. 2191
52.46. pg_shdepend .............................................................................. 2191
52.47. pg_shdescription .................................................................... 2193
52.48. pg_shseclabel .......................................................................... 2193
52.49. pg_statistic ............................................................................ 2194
52.50. pg_statistic_ext .................................................................... 2195
52.51. pg_statistic_ext_data .......................................................... 2196
52.52. pg_subscription ...................................................................... 2196
52.53. pg_subscription_rel .............................................................. 2197
52.54. pg_tablespace .......................................................................... 2197
52.55. pg_transform ............................................................................ 2198
52.56. pg_trigger ................................................................................ 2198
xvi

52.57. pg_ts_config ............................................................................ 2200
52.58. pg_ts_config_map .................................................................... 2200
52.59. pg_ts_dict ................................................................................ 2201
52.60. pg_ts_parser ............................................................................ 2201
52.61. pg_ts_template ........................................................................ 2202
52.62. pg_type ...................................................................................... 2202
52.63. pg_user_mapping ...................................................................... 2205
52.64. System Views ................................................................................ 2206
52.65. pg_available_extensions ...................................................... 2207
52.66. pg_available_extension_versions ...................................... 2207
52.67. pg_backend_memory_contexts ................................................ 2208
52.68. pg_config .................................................................................. 2209
52.69. pg_cursors ................................................................................ 2209
52.70. pg_file_settings .................................................................... 2210
52.71. pg_group .................................................................................... 2211
52.72. pg_hba_file_rules .................................................................. 2211
52.73. pg_indexes ................................................................................ 2212
52.74. pg_locks .................................................................................... 2212
52.75. pg_matviews .............................................................................. 2215
52.76. pg_policies .............................................................................. 2215
52.77. pg_prepared_statements ........................................................ 2216
52.78. pg_prepared_xacts .................................................................. 2216
52.79. pg_publication_tables .......................................................... 2217
52.80. pg_replication_origin_status ............................................ 2217
52.81. pg_replication_slots ............................................................ 2218
52.82. pg_roles .................................................................................... 2219
52.83. pg_rules .................................................................................... 2220
52.84. pg_seclabels ............................................................................ 2220
52.85. pg_sequences ............................................................................ 2221
52.86. pg_settings .............................................................................. 2221
52.87. pg_shadow .................................................................................. 2224
52.88. pg_shmem_allocations ............................................................ 2224
52.89. pg_stats .................................................................................... 2225
52.90. pg_stats_ext ............................................................................ 2226
52.91. pg_stats_ext_exprs ................................................................ 2227
52.92. pg_tables .................................................................................. 2229
52.93. pg_timezone_abbrevs .............................................................. 2229
52.94. pg_timezone_names .................................................................. 2230
52.95. pg_user ...................................................................................... 2230
52.96. pg_user_mappings .................................................................... 2231
52.97. pg_views .................................................................................... 2231
53. Frontend/Backend Protocol ........................................................................... 2233
53.1. Overview ........................................................................................ 2233
53.2. Message Flow .................................................................................. 2234
53.3. SASL Authentication ........................................................................ 2248
53.4. Streaming Replication Protocol ........................................................... 2250
53.5. Logical Streaming Replication Protocol ................................................ 2257
53.6. Message Data Types ......................................................................... 2258
53.7. Message Formats .............................................................................. 2258
53.8. Error and Notice Message Fields ......................................................... 2275
53.9. Logical Replication Message Formats .................................................. 2277
53.10. Summary of Changes since Protocol 2.0 ............................................. 2283
54. PostgreSQL Coding Conventions ................................................................... 2285
54.1. Formatting ....................................................................................... 2285
54.2. Reporting Errors Within the Server ...................................................... 2285
54.3. Error Message Style Guide ................................................................. 2289
54.4. Miscellaneous Coding Conventions ...................................................... 2293
55. Native Language Support ............................................................................. 2295
xvii

55.1. For the Translator ............................................................................. 2295
55.2. For the Programmer .......................................................................... 2297
56. Writing a Procedural Language Handler .......................................................... 2301
57. Writing a Foreign Data Wrapper .................................................................... 2303
57.1. Foreign Data Wrapper Functions ......................................................... 2303
57.2. Foreign Data Wrapper Callback Routines .............................................. 2303
57.3. Foreign Data Wrapper Helper Functions ............................................... 2319
57.4. Foreign Data Wrapper Query Planning ................................................. 2320
57.5. Row Locking in Foreign Data Wrappers ............................................... 2322
58. Writing a Table Sampling Method ................................................................. 2324
58.1. Sampling Method Support Functions .................................................... 2324
59. Writing a Custom Scan Provider .................................................................... 2327
59.1. Creating Custom Scan Paths ............................................................... 2327
59.2. Creating Custom Scan Plans ............................................................... 2328
59.3. Executing Custom Scans .................................................................... 2329
60. Genetic Query Optimizer .............................................................................. 2332
60.1. Query Handling as a Complex Optimization Problem .............................. 2332
60.2. Genetic Algorithms ........................................................................... 2332
60.3. Genetic Query Optimization (GEQO) in PostgreSQL .............................. 2333
60.4. Further Reading ............................................................................... 2335
61. Table Access Method Interface Definition ....................................................... 2336
62. Index Access Method Interface Definition ....................................................... 2337
62.1. Basic API Structure for Indexes .......................................................... 2337
62.2. Index Access Method Functions .......................................................... 2340
62.3. Index Scanning ................................................................................ 2345
62.4. Index Locking Considerations ............................................................. 2347
62.5. Index Uniqueness Checks .................................................................. 2348
62.6. Index Cost Estimation Functions ......................................................... 2349
63. Generic WAL Records ................................................................................. 2352
64. B-Tree Indexes ........................................................................................... 2354
64.1. Introduction ..................................................................................... 2354
64.2. Behavior of B-Tree Operator Classes ................................................... 2354
64.3. B-Tree Support Functions .................................................................. 2355
64.4. Implementation ................................................................................ 2358
65. GiST Indexes ............................................................................................. 2361
65.1. Introduction ..................................................................................... 2361
65.2. Built-in Operator Classes ................................................................... 2361
65.3. Extensibility .................................................................................... 2364
65.4. Implementation ................................................................................ 2377
65.5. Examples ........................................................................................ 2377
66. SP-GiST Indexes ........................................................................................ 2379
66.1. Introduction ..................................................................................... 2379
66.3. Extensibility .................................................................................... 2381
66.4. Implementation ................................................................................ 2390
66.5. Examples ........................................................................................ 2391
67. GIN Indexes .............................................................................................. 2392
67.1. Introduction ..................................................................................... 2392
67.3. Extensibility .................................................................................... 2393
67.4. Implementation ................................................................................ 2395
67.5. GIN Tips and Tricks ......................................................................... 2397
67.6. Limitations ...................................................................................... 2397
67.7. Examples ........................................................................................ 2398
68. BRIN Indexes ............................................................................................ 2399
68.1. Introduction ..................................................................................... 2399
68.3. Extensibility .................................................................................... 2407
xviii

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