The catalog pg_foreign_data_wrapper stores foreign-data wrapper definitions. A foreign-data wrapper is the mechanism by which external data, residing on foreign servers, is accessed. Table 50-23. pg_foreign_data_wrapper Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) fdwname name Name of the foreign-data wrapper fdwowner oid pg_authid.oid Owner of the foreign-data wrapper fdwhandler oid pg_proc.oid References a handler functi

The view pg_file_settings provides a summary of the contents of the server's configuration file(s). A row appears in this view for each "name = value" entry appearing in the files, with annotations indicating whether the value could be applied successfully. Additional row(s) may appear for problems not linked to a "name = value" entry, such as syntax errors in the files. This view is helpful for checking whether planned changes in the configuration files will work, or for diagnosing a previous

The catalog pg_extension stores information about the installed extensions. See Section 36.15 for details about extensions. Table 50-22. pg_extension Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) extname name Name of the extension extowner oid pg_authid.oid Owner of the extension extnamespace oid pg_namespace.oid Schema containing the extension's exported objects extrelocatable bool True if extension can be relocated to a

The catalog pg_event_trigger stores event triggers. See Chapter 38 for more information. Table 50-21. pg_event_trigger Columns Name Type References Description evtname name Trigger name (must be unique) evtevent name Identifies the event for which this trigger fires evtowner oid pg_authid.oid Owner of the event trigger evtfoid oid pg_proc.oid The function to be called evtenabled char Controls in which session_replication_role modes the event trigger fires. O = trigger fires in "origin"

The pg_enum catalog contains entries showing the values and labels for each enum type. The internal representation of a given enum value is actually the OID of its associated row in pg_enum. Table 50-20. pg_enum Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) enumtypid oid pg_type.oid The OID of the pg_type entry owning this enum value enumsortorder float4 The sort position of this enum value within its enum type enumlabel na

The catalog pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the COMMENT command and viewed with psql's \d commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description. See also pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a database cluster. Table 50-19. pg_description Columns Name Type References Description ob

The catalog pg_depend records the dependency relationships between database objects. This information allows DROP commands to find which other objects must be dropped by DROP CASCADE or prevent dropping in the DROP RESTRICT case. See also pg_shdepend, which performs a similar function for dependencies involving objects that are shared across a database cluster. Table 50-18. pg_depend Columns Name Type References Description classid oid pg_class.oid The OID of the system catalog the dependent

The catalog pg_default_acl stores initial privileges to be assigned to newly created objects. Table 50-17. pg_default_acl Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly selected) defaclrole oid pg_authid.oid The OID of the role associated with this entry defaclnamespace oid pg_namespace.oid The OID of the namespace associated with this entry, or 0 if none defaclobjtype char Type of object this entry is for: r = relation (table, view),

The catalog pg_db_role_setting records the default values that have been set for run-time configuration variables, for each role and database combination. Unlike most system catalogs, pg_db_role_setting is shared across all databases of a cluster: there is only one copy of pg_db_role_setting per cluster, not one per database. Table 50-16. pg_db_role_setting Columns Name Type References Description setdatabase oid pg_database.oid The OID of the database the setting is applicable to, or zero if

The catalog pg_database stores information about the available databases. Databases are created with the CREATE DATABASE command. Consult Chapter 22 for details about the meaning of some of the parameters. Unlike most system catalogs, pg_database is shared across all databases of a cluster: there is only one copy of pg_database per cluster, not one per database. Table 50-15. pg_database Columns Name Type References Description oid oid Row identifier (hidden attribute; must be explicitly sel