Chapter 43. System Catalogs

Table of Contents
43.1. Overview
43.2. pg_aggregate
43.3. pg_am
43.4. pg_amop
43.5. pg_amproc
43.6. pg_attrdef
43.7. pg_attribute
43.8. pg_cast
43.9. pg_class
43.10. pg_constraint
43.11. pg_conversion
43.12. pg_database
43.13. pg_depend
43.14. pg_description
43.15. pg_group
43.16. pg_index
43.17. pg_inherits
43.18. pg_language
43.19. pg_largeobject
43.20. pg_listener
43.21. pg_namespace
43.22. pg_opclass
43.23. pg_operator
43.24. pg_proc
43.25. pg_rewrite
43.26. pg_shadow
43.27. pg_statistic
43.28. pg_trigger
43.29. pg_type
43.30. System Views
43.31. pg_indexes
43.32. pg_locks
43.33. pg_rules
43.34. pg_settings
43.35. pg_stats
43.36. pg_tables
43.37. pg_user
43.38. pg_views

The system catalogs are the place where a relational database management system stores schema metadata, such as information about tables and columns, and internal bookkeeping information. PostgreSQL's system catalogs are regular tables. You can drop and recreate the tables, add columns, insert and update values, and severely mess up your system that way. Normally, one should not change the system catalogs by hand, there are always SQL commands to do that. (For example, CREATE DATABASE inserts a row into the pg_database catalog --- and actually creates the database on disk.) There are some exceptions for particularly esoteric operations, such as adding index access methods.

43.1. Overview

Table 43-1 lists the system catalogs. More detailed documentation of each catalog follows below.

Most system catalogs are copied from the template database during database creation and are thereafter database-specific. A few catalogs are physically shared across all databases in a cluster; these are marked in the descriptions of the individual catalogs.

Table 43-1. System Catalogs

Catalog NamePurpose
pg_aggregateaggregate functions
pg_amindex access methods
pg_amopaccess method operators
pg_amprocaccess method support procedures
pg_attrdefcolumn default values
pg_attributetable columns ("attributes")
pg_castcasts (data type conversions)
pg_classtables, indexes, sequences ("relations")
pg_constraintcheck constraints, unique constraints, primary key constraints, foreign key constraints
pg_conversionencoding conversion information
pg_databasedatabases within this database cluster
pg_dependdependencies between database objects
pg_descriptiondescriptions or comments on database objects
pg_groupgroups of database users
pg_indexadditional index information
pg_inheritstable inheritance hierarchy
pg_languagelanguages for writing functions
pg_largeobjectlarge objects
pg_listenerasynchronous notification support
pg_opclassindex access method operator classes
pg_procfunctions and procedures
pg_rewritequery rewrite rules
pg_shadowdatabase users
pg_statisticplanner statistics
pg_typedata types