The functions described in this section are used to obtain various information about a PostgreSQL installation. shows several functions that extract session and system information. In addition to the functions listed in this section, there are a number of functions related to the statistics system that also provide system information. See for more information. Function Description current_catalog current_catalog name current_database current_database () name Returns the name of the current database. (Databases are called catalogs in the SQL standard, so current_catalog is the standard's spelling.) current_query current_query () text Returns the text of the currently executing query, as submitted by the client (which might contain more than one statement). current_role current_role name This is equivalent to current_user. current_schema schema current current_schema name current_schema () name Returns the name of the schema that is first in the search path (or a null value if the search path is empty). This is the schema that will be used for any tables or other named objects that are created without specifying a target schema. current_schemas search path current current_schemas ( include_implicit boolean ) name[] Returns an array of the names of all schemas presently in the effective search path, in their priority order. (Items in the current setting that do not correspond to existing, searchable schemas are omitted.) If the Boolean argument is true, then implicitly-searched system schemas such as pg_catalog are included in the result. current_user user current current_user name Returns the user name of the current execution context. inet_client_addr inet_client_addr () inet Returns the IP address of the current client, or NULL if the current connection is via a Unix-domain socket. inet_client_port inet_client_port () integer Returns the IP port number of the current client, or NULL if the current connection is via a Unix-domain socket. inet_server_addr inet_server_addr () inet Returns the IP address on which the server accepted the current connection, or NULL if the current connection is via a Unix-domain socket. inet_server_port inet_server_port () integer Returns the IP port number on which the server accepted the current connection, or NULL if the current connection is via a Unix-domain socket. pg_backend_pid pg_backend_pid () integer Returns the process ID of the server process attached to the current session. pg_blocking_pids pg_blocking_pids ( integer ) integer[] Returns an array of the process ID(s) of the sessions that are blocking the server process with the specified process ID from acquiring a lock, or an empty array if there is no such server process or it is not blocked. One server process blocks another if it either holds a lock that conflicts with the blocked process's lock request (hard block), or is waiting for a lock that would conflict with the blocked process's lock request and is ahead of it in the wait queue (soft block). When using parallel queries the result always lists client-visible process IDs (that is, pg_backend_pid results) even if the actual lock is held or awaited by a child worker process. As a result of that, there may be duplicated PIDs in the result. Also note that when a prepared transaction holds a conflicting lock, it will be represented by a zero process ID. Frequent calls to this function could have some impact on database performance, because it needs exclusive access to the lock manager's shared state for a short time. pg_conf_load_time pg_conf_load_time () timestamp with time zone Returns the time when the server configuration files were last loaded. If the current session was alive at the time, this will be the time when the session itself re-read the configuration files (so the reading will vary a little in different sessions). Otherwise it is the time when the postmaster process re-read the configuration files. pg_current_logfile Logging pg_current_logfile function current_logfiles and the pg_current_logfile function Logging current_logfiles file and the pg_current_logfile function pg_current_logfile ( text ) text Returns the path name of the log file currently in use by the logging collector. The path includes the directory and the individual log file name. The result is NULL if the logging collector is disabled. When multiple log files exist, each in a different format, pg_current_logfile without an argument returns the path of the file having the first format found in the ordered list: stderr, csvlog, jsonlog. NULL is returned if no log file has any of these formats. To request information about a specific log file format, supply either csvlog, jsonlog or stderr as the value of the optional parameter. The result is NULL if the log format requested is not configured in . The result reflects the contents of the current_logfiles file. This function is restricted to superusers and roles with privileges of the pg_monitor role by default, but other users can be granted EXECUTE to run the function. pg_get_loaded_modules pg_get_loaded_modules () setof record ( module_name text, version text, file_name text ) Returns a list of the loadable modules that are loaded into the current server session. The module_name and version fields are NULL unless the module author supplied values for them using the PG_MODULE_MAGIC_EXT macro. The file_name field gives the file name of the module (shared library). pg_my_temp_schema pg_my_temp_schema () oid Returns the OID of the current session's temporary schema, or zero if it has none (because it has not created any temporary tables). pg_is_other_temp_schema pg_is_other_temp_schema ( oid ) boolean Returns true if the given OID is the OID of another session's temporary schema. (This can be useful, for example, to exclude other sessions' temporary tables from a catalog display.) pg_jit_available pg_jit_available () boolean Returns true if a JIT compiler extension is available (see ) and the configuration parameter is set to on. pg_numa_available pg_numa_available () boolean Returns true if the server has been compiled with NUMA support. pg_listening_channels pg_listening_channels () setof text Returns the set of names of asynchronous notification channels that the current session is listening to. pg_notification_queue_usage pg_notification_queue_usage () double precision Returns the fraction (0–1) of the asynchronous notification queue's maximum size that is currently occupied by notifications that are waiting to be processed. See and for more information. pg_postmaster_start_time pg_postmaster_start_time () timestamp with time zone Returns the time when the server started. pg_safe_snapshot_blocking_pids pg_safe_snapshot_blocking_pids ( integer ) integer[] Returns an array of the process ID(s) of the sessions that are blocking the server process with the specified process ID from acquiring a safe snapshot, or an empty array if there is no such server process or it is not blocked. A session running a SERIALIZABLE transaction blocks a SERIALIZABLE READ ONLY DEFERRABLE transaction from acquiring a snapshot until the latter determines that it is safe to avoid taking any predicate locks. See for more information about serializable and deferrable transactions. Frequent calls to this function could have some impact on database performance, because it needs access to the predicate lock manager's shared state for a short time. pg_trigger_depth pg_trigger_depth () integer Returns the current nesting level of PostgreSQL triggers (0 if not called, directly or indirectly, from inside a trigger). session_user session_user name Returns the session user's name. system_user system_user text Returns the authentication method and the identity (if any) that the user presented during the authentication cycle before they were assigned a database role. It is represented as auth_method:identity or NULL if the user has not been authenticated (for example if Trust authentication has been used). user user name This is equivalent to current_user. current_catalog, current_role, current_schema, current_user, session_user, and user have special syntactic status in SQL: they must be called without trailing parentheses. In PostgreSQL, parentheses can optionally be used with current_schema, but not with the others. The session_user is normally the user who initiated the current database connection; but superusers can change this setting with . The current_user is the user identifier that is applicable for permission checking. Normally it is equal to the session user, but it can be changed with . It also changes during the execution of functions with the attribute SECURITY DEFINER. In Unix parlance, the session user is the real user and the current user is the effective user. current_role and user are synonyms for current_user. (The SQL standard draws a distinction between current_role and current_user, but PostgreSQL does not, since it unifies users and roles into a single kind of entity.) privilege querying lists functions that allow querying object access privileges programmatically. (See for more information about privileges.) In these functions, the user whose privileges are being inquired about can be specified by name or by OID (pg_authid.oid), or if the name is given as public then the privileges of the PUBLIC pseudo-role are checked. Also, the user argument can be omitted entirely, in which case the current_user is assumed. The object that is being inquired about can be specified either by name or by OID, too. When specifying by name, a schema name can be included if relevant. The access privilege of interest is specified by a text string, which must evaluate to one of the appropriate privilege keywords for the object's type (e.g., SELECT). Optionally, WITH GRANT OPTION can be added to a privilege type to test whether the privilege is held with grant option. Also, multiple privilege types can be listed separated by commas, in which case the result will be true if any of the listed privileges is held. (Case of the privilege string is not significant, and extra whitespace is allowed between but not within privilege names.) Some examples: SELECT has_table_privilege('myschema.mytable', 'select'); SELECT has_table_privilege('joe', 'mytable', 'INSERT, SELECT WITH GRANT OPTION'); Function Description has_any_column_privilege has_any_column_privilege ( user name or oid, table text or oid, privilege text ) boolean Does user have privilege for any column of table? This succeeds either if the privilege is held for the whole table, or if there is a column-level grant of the privilege for at least one column. Allowable privilege types are SELECT, INSERT, UPDATE, and REFERENCES. has_column_privilege has_column_privilege ( user name or oid, table text or oid, column text or smallint, privilege text ) boolean Does user have privilege for the specified table column? This succeeds either if the privilege is held for the whole table, or if there is a column-level grant of the privilege for the column. The column can be specified by name or by attribute number (pg_attribute.attnum). Allowable privilege types are SELECT, INSERT, UPDATE, and REFERENCES. has_database_privilege has_database_privilege ( user name or oid, database text or oid, privilege text ) boolean Does user have privilege for database? Allowable privilege types are CREATE, CONNECT, TEMPORARY, and TEMP (which is equivalent to TEMPORARY). has_foreign_data_wrapper_privilege has_foreign_data_wrapper_privilege ( user name or oid, fdw text or oid, privilege text ) boolean Does user have privilege for foreign-data wrapper? The only allowable privilege type is USAGE. has_function_privilege has_function_privilege ( user name or oid, function text or oid, privilege text ) boolean Does user have privilege for function? The only allowable privilege type is EXECUTE. When specifying a function by name rather than by OID, the allowed input is the same as for the regprocedure data type (see ). An example is: SELECT has_function_privilege('joeuser', 'myfunc(int, text)', 'execute'); has_language_privilege has_language_privilege ( user name or oid, language text or oid, privilege text ) boolean Does user have privilege for language? The only allowable privilege type is USAGE. has_largeobject_privilege has_largeobject_privilege ( user name or oid, largeobject oid, privilege text ) boolean Does user have privilege for large object? Allowable privilege types are SELECT and UPDATE. has_parameter_privilege has_parameter_privilege ( user name or oid, parameter text, privilege text ) boolean Does user have privilege for configuration parameter? The parameter name is case-insensitive. Allowable privilege types are SET and ALTER SYSTEM. has_schema_privilege has_schema_privilege ( user name or oid, schema text or oid, privilege text ) boolean Does user have privilege for schema? Allowable privilege types are CREATE and USAGE. has_sequence_privilege has_sequence_privilege ( user name or oid, sequence text or oid, privilege text ) boolean Does user have privilege for sequence? Allowable privilege types are USAGE, SELECT, and UPDATE. has_server_privilege has_server_privilege ( user name or oid, server text or oid, privilege text ) boolean Does user have privilege for foreign server? The only allowable privilege type is USAGE. has_table_privilege has_table_privilege ( user name or oid, table text or oid, privilege text ) boolean Does user have privilege for table? Allowable privilege types are SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER, and MAINTAIN. has_tablespace_privilege has_tablespace_privilege ( user name or oid, tablespace text or oid, privilege text ) boolean Does user have privilege for tablespace? The only allowable privilege type is CREATE. has_type_privilege has_type_privilege ( user name or oid, type text or oid, privilege text ) boolean Does user have privilege for data type? The only allowable privilege type is USAGE. When specifying a type by name rather than by OID, the allowed input is the same as for the regtype data type (see ). pg_has_role pg_has_role ( user name or oid, role text or oid, privilege text ) boolean Does user have privilege for role? Allowable privilege types are MEMBER, USAGE, and SET. MEMBER denotes direct or indirect membership in the role without regard to what specific privileges may be conferred. USAGE denotes whether the privileges of the role are immediately available without doing SET ROLE, while SET denotes whether it is possible to change to the role using the SET ROLE command. WITH ADMIN OPTION or WITH GRANT OPTION can be added to any of these privilege types to test whether the ADMIN privilege is held (all six spellings test the same thing). This function does not allow the special case of setting user to public, because the PUBLIC pseudo-role can never be a member of real roles. row_security_active row_security_active ( table text or oid ) boolean Is row-level security active for the specified table in the context of the current user and current environment? shows the operators available for the aclitem type, which is the catalog representation of access privileges. See for information about how to read access privilege values. Operator Description Example(s) aclitemeq aclitem = aclitem boolean Are aclitems equal? (Notice that type aclitem lacks the usual set of comparison operators; it has only equality. In turn, aclitem arrays can only be compared for equality.) 'calvin=r*w/hobbes'::aclitem = 'calvin=r*w*/hobbes'::aclitem f aclcontains aclitem[] @> aclitem boolean Does array contain the specified privileges? (This is true if there is an array entry that matches the aclitem's grantee and grantor, and has at least the specified set of privileges.) '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] @> 'calvin=r*/hobbes'::aclitem t aclitem[] ~ aclitem boolean This is a deprecated alias for @>. '{calvin=r*w/hobbes,hobbes=r*w*/postgres}'::aclitem[] ~ 'calvin=r*/hobbes'::aclitem t shows some additional functions to manage the aclitem type. Function Description acldefault acldefault ( type "char", ownerId oid ) aclitem[] Constructs an aclitem array holding the default access privileges for an object of type type belonging to the role with OID ownerId. This represents the access privileges that will be assumed when an object's ACL entry is null. (The default access privileges are described in .) The type parameter must be one of 'c' for COLUMN, 'r' for TABLE and table-like objects, 's' for SEQUENCE, 'd' for DATABASE, 'f' for FUNCTION or PROCEDURE, 'l' for LANGUAGE, 'L' for LARGE OBJECT, 'n' for SCHEMA, 'p' for PARAMETER, 't' for TABLESPACE, 'F' for FOREIGN DATA WRAPPER, 'S' for FOREIGN SERVER, or 'T' for TYPE or DOMAIN. aclexplode aclexplode ( aclitem[] ) setof record ( grantor oid, grantee oid, privilege_type text, is_grantable boolean ) Returns the aclitem array as a set of rows. If the grantee is the pseudo-role PUBLIC, it is represented by zero in the grantee column. Each granted privilege is represented as SELECT, INSERT, etc (see for a full list). Note that each privilege is broken out as a separate row, so only one keyword appears in the privilege_type column. makeaclitem makeaclitem ( grantee oid, grantor oid, privileges text, is_grantable boolean ) aclitem Constructs an aclitem with the given properties. privileges is a comma-separated list of privilege names such as SELECT, INSERT, etc, all of which are set in the result. (Case of the privilege string is not significant, and extra whitespace is allowed between but not within privilege names.) shows functions that determine whether a certain object is visible in the current schema search path. For example, a table is said to be visible if its containing schema is in the search path and no table of the same name appears earlier in the search path. This is equivalent to the statement that the table can be referenced by name without explicit schema qualification. Thus, to list the names of all visible tables: SELECT relname FROM pg_class WHERE pg_table_is_visible(oid); For functions and operators, an object in the search path is said to be visible if there is no object of the same name and argument data type(s) earlier in the path. For operator classes and families, both the name and the associated index access method are considered. search path object visibility Function Description pg_collation_is_visible pg_collation_is_visible ( collation oid ) boolean Is collation visible in search path? pg_conversion_is_visible pg_conversion_is_visible ( conversion oid ) boolean Is conversion visible in search path? pg_function_is_visible pg_function_is_visible ( function oid ) boolean Is function visible in search path? (This also works for procedures and aggregates.) pg_opclass_is_visible pg_opclass_is_visible ( opclass oid ) boolean Is operator class visible in search path? pg_operator_is_visible pg_operator_is_visible ( operator oid ) boolean Is operator visible in search path? pg_opfamily_is_visible pg_opfamily_is_visible ( opclass oid ) boolean Is operator family visible in search path? pg_statistics_obj_is_visible pg_statistics_obj_is_visible ( stat oid ) boolean Is statistics object visible in search path? pg_table_is_visible pg_table_is_visible ( table oid ) boolean Is table visible in search path? (This works for all types of relations, including views, materialized views, indexes, sequences and foreign tables.) pg_ts_config_is_visible pg_ts_config_is_visible ( config oid ) boolean Is text search configuration visible in search path? pg_ts_dict_is_visible pg_ts_dict_is_visible ( dict oid ) boolean Is text search dictionary visible in search path? pg_ts_parser_is_visible pg_ts_parser_is_visible ( parser oid ) boolean Is text search parser visible in search path? pg_ts_template_is_visible pg_ts_template_is_visible ( template oid ) boolean Is text search template visible in search path? pg_type_is_visible pg_type_is_visible ( type oid ) boolean Is type (or domain) visible in search path? All these functions require object OIDs to identify the object to be checked. If you want to test an object by name, it is convenient to use the OID alias types (regclass, regtype, regprocedure, regoperator, regconfig, or regdictionary), for example: SELECT pg_type_is_visible('myschema.widget'::regtype); Note that it would not make much sense to test a non-schema-qualified type name in this way — if the name can be recognized at all, it must be visible. lists functions that extract information from the system catalogs. Function Description format_type format_type ( type oid, typemod integer ) text Returns the SQL name for a data type that is identified by its type OID and possibly a type modifier. Pass NULL for the type modifier if no specific modifier is known. pg_basetype pg_basetype ( regtype ) regtype Returns the OID of the base type of a domain identified by its type OID. If the argument is the OID of a non-domain type, returns the argument as-is. Returns NULL if the argument is not a valid type OID. If there's a chain of domain dependencies, it will recurse until finding the base type. Assuming CREATE DOMAIN mytext AS text: pg_basetype('mytext'::regtype) text pg_char_to_encoding pg_char_to_encoding ( encoding name ) integer Converts the supplied encoding name into an integer representing the internal identifier used in some system catalog tables. Returns -1 if an unknown encoding name is provided. pg_encoding_to_char pg_encoding_to_char ( encoding integer ) name Converts the integer used as the internal identifier of an encoding in some system catalog tables into a human-readable string. Returns an empty string if an invalid encoding number is provided. pg_get_catalog_foreign_keys pg_get_catalog_foreign_keys () setof record ( fktable regclass, fkcols text[], pktable regclass, pkcols text[], is_array boolean, is_opt boolean ) Returns a set of records describing the foreign key relationships that exist within the PostgreSQL system catalogs. The fktable column contains the name of the referencing catalog, and the fkcols column contains the name(s) of the referencing column(s). Similarly, the pktable column contains the name of the referenced catalog, and the pkcols column contains the name(s) of the referenced column(s). If is_array is true, the last referencing column is an array, each of whose elements should match some entry in the referenced catalog. If is_opt is true, the referencing column(s) are allowed to contain zeroes instead of a valid reference. pg_get_constraintdef pg_get_constraintdef ( constraint oid , pretty boolean ) text Reconstructs the creating command for a constraint. (This is a decompiled reconstruction, not the original text of the command.) pg_get_expr pg_get_expr ( expr pg_node_tree, relation oid , pretty boolean ) text Decompiles the internal form of an expression stored in the system catalogs, such as the default value for a column. If the expression might contain Vars, specify the OID of the relation they refer to as the second parameter; if no Vars are expected, passing zero is sufficient. pg_get_functiondef pg_get_functiondef ( func oid ) text Reconstructs the creating command for a function or procedure. (This is a decompiled reconstruction, not the original text of the command.) The result is a complete CREATE OR REPLACE FUNCTION or CREATE OR REPLACE PROCEDURE statement. pg_get_function_arguments pg_get_function_arguments ( func oid ) text Reconstructs the argument list of a function or procedure, in the form it would need to appear in within CREATE FUNCTION (including default values). pg_get_function_identity_arguments pg_get_function_identity_arguments ( func oid ) text Reconstructs the argument list necessary to identify a function or procedure, in the form it would need to appear in within commands such as ALTER FUNCTION. This form omits default values. pg_get_function_result pg_get_function_result ( func oid ) text Reconstructs the RETURNS clause of a function, in the form it would need to appear in within CREATE FUNCTION. Returns NULL for a procedure. pg_get_indexdef pg_get_indexdef ( index oid , column integer, pretty boolean ) text Reconstructs the creating command for an index. (This is a decompiled reconstruction, not the original text of the command.) If column is supplied and is not zero, only the definition of that column is reconstructed. pg_get_keywords pg_get_keywords () setof record ( word text, catcode "char", barelabel boolean, catdesc text, baredesc text ) Returns a set of records describing the SQL keywords recognized by the server. The word column contains the keyword. The catcode column contains a category code: U for an unreserved keyword, C for a keyword that can be a column name, T for a keyword that can be a type or function name, or R for a fully reserved keyword. The barelabel column contains true if the keyword can be used as a bare column label in SELECT lists, or false if it can only be used after AS. The catdesc column contains a possibly-localized string describing the keyword's category. The baredesc column contains a possibly-localized string describing the keyword's column label status. pg_get_partkeydef pg_get_partkeydef ( table oid ) text Reconstructs the definition of a partitioned table's partition key, in the form it would have in the PARTITION BY clause of CREATE TABLE. (This is a decompiled reconstruction, not the original text of the command.) pg_get_ruledef pg_get_ruledef ( rule oid , pretty boolean ) text Reconstructs the creating command for a rule. (This is a decompiled reconstruction, not the original text of the command.) pg_get_serial_sequence pg_get_serial_sequence ( table text, column text ) text Returns the name of the sequence associated with a column, or NULL if no sequence is associated with the column. If the column is an identity column, the associated sequence is the sequence internally created for that column. For columns created using one of the serial types (serial, smallserial, bigserial), it is the sequence created for that serial column definition. In the latter case, the association can be modified or removed with ALTER SEQUENCE OWNED BY. (This function probably should have been called pg_get_owned_sequence; its current name reflects the fact that it has historically been used with serial-type columns.) The first parameter is a table name with optional schema, and the second parameter is a column name. Because the first parameter potentially contains both schema and table names, it is parsed per usual SQL rules, meaning it is lower-cased by default. The second parameter, being just a column name, is treated literally and so has its case preserved. The result is suitably formatted for passing to the sequence functions (see ). A typical use is in reading the current value of the sequence for an identity or serial column, for example: SELECT currval(pg_get_serial_sequence('sometable', 'id')); pg_get_statisticsobjdef pg_get_statisticsobjdef ( statobj oid ) text Reconstructs the creating command for an extended statistics object. (This is a decompiled reconstruction, not the original text of the command.) pg_get_triggerdef pg_get_triggerdef ( trigger oid , pretty boolean ) text Reconstructs the creating command for a trigger. (This is a decompiled reconstruction, not the original text of the command.) pg_get_userbyid pg_get_userbyid ( role oid ) name Returns a role's name given its OID. pg_get_viewdef pg_get_viewdef ( view oid , pretty boolean ) text Reconstructs the underlying SELECT command for a view or materialized view. (This is a decompiled reconstruction, not the original text of the command.) pg_get_viewdef ( view oid, wrap_column integer ) text Reconstructs the underlying SELECT command for a view or materialized view. (This is a decompiled reconstruction, not the original text of the command.) In this form of the function, pretty-printing is always enabled, and long lines are wrapped to try to keep them shorter than the specified number of columns. pg_get_viewdef ( view text , pretty boolean ) text Reconstructs the underlying SELECT command for a view or materialized view, working from a textual name for the view rather than its OID. (This is deprecated; use the OID variant instead.) pg_index_column_has_property pg_index_column_has_property ( index regclass, column integer, property text ) boolean Tests whether an index column has the named property. Common index column properties are listed in . (Note that extension access methods can define additional property names for their indexes.) NULL is returned if the property name is not known or does not apply to the particular object, or if the OID or column number does not identify a valid object. pg_index_has_property pg_index_has_property ( index regclass, property text ) boolean Tests whether an index has the named property. Common index properties are listed in . (Note that extension access methods can define additional property names for their indexes.) NULL is returned if the property name is not known or does not apply to the particular object, or if the OID does not identify a valid object. pg_indexam_has_property pg_indexam_has_property ( am oid, property text ) boolean Tests whether an index access method has the named property. Access method properties are listed in . NULL is returned if the property name is not known or does not apply to the particular object, or if the OID does not identify a valid object. pg_options_to_table pg_options_to_table ( options_array text[] ) setof record ( option_name text, option_value text ) Returns the set of storage options represented by a value from pg_class.reloptions or pg_attribute.attoptions. pg_settings_get_flags pg_settings_get_flags ( guc text ) text[] Returns an array of the flags associated with the given GUC, or NULL if it does not exist. The result is an empty array if the GUC exists but there are no flags to show. Only the most useful flags listed in are exposed. pg_tablespace_databases pg_tablespace_databases ( tablespace oid ) setof oid Returns the set of OIDs of databases that have objects stored in the specified tablespace. If this function returns any rows, the tablespace is not empty and cannot be dropped. To identify the specific objects populating the tablespace, you will need to connect to the database(s) identified by pg_tablespace_databases and query their pg_class catalogs. pg_tablespace_location pg_tablespace_location ( tablespace oid ) text Returns the file system path that this tablespace is located in. pg_typeof pg_typeof ( "any" ) regtype Returns the OID of the data type of the value that is passed to it. This can be helpful for troubleshooting or dynamically constructing SQL queries. The function is declared as returning regtype, which is an OID alias type (see ); this means that it is the same as an OID for comparison purposes but displays as a type name. pg_typeof(33) integer COLLATION FOR COLLATION FOR ( "any" ) text Returns the name of the collation of the value that is passed to it. The value is quoted and schema-qualified if necessary. If no collation was derived for the argument expression, then NULL is returned. If the argument is not of a collatable data type, then an error is raised. collation for ('foo'::text) "default" collation for ('foo' COLLATE "de_DE") "de_DE" to_regclass to_regclass ( text ) regclass Translates a textual relation name to its OID. A similar result is obtained by casting the string to type regclass (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regdatabase to_regdatabase ( text ) regdatabase Translates a textual database name to its OID. A similar result is obtained by casting the string to type regdatabase (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regcollation to_regcollation ( text ) regcollation Translates a textual collation name to its OID. A similar result is obtained by casting the string to type regcollation (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regnamespace to_regnamespace ( text ) regnamespace Translates a textual schema name to its OID. A similar result is obtained by casting the string to type regnamespace (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regoper to_regoper ( text ) regoper Translates a textual operator name to its OID. A similar result is obtained by casting the string to type regoper (see ); however, this function will return NULL rather than throwing an error if the name is not found or is ambiguous. to_regoperator to_regoperator ( text ) regoperator Translates a textual operator name (with parameter types) to its OID. A similar result is obtained by casting the string to type regoperator (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regproc to_regproc ( text ) regproc Translates a textual function or procedure name to its OID. A similar result is obtained by casting the string to type regproc (see ); however, this function will return NULL rather than throwing an error if the name is not found or is ambiguous. to_regprocedure to_regprocedure ( text ) regprocedure Translates a textual function or procedure name (with argument types) to its OID. A similar result is obtained by casting the string to type regprocedure (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regrole to_regrole ( text ) regrole Translates a textual role name to its OID. A similar result is obtained by casting the string to type regrole (see ); however, this function will return NULL rather than throwing an error if the name is not found. to_regtype to_regtype ( text ) regtype Parses a string of text, extracts a potential type name from it, and translates that name into a type OID. A syntax error in the string will result in an error; but if the string is a syntactically valid type name that happens not to be found in the catalogs, the result is NULL. A similar result is obtained by casting the string to type regtype (see ), except that that will throw error for name not found. to_regtypemod to_regtypemod ( text ) integer Parses a string of text, extracts a potential type name from it, and translates its type modifier, if any. A syntax error in the string will result in an error; but if the string is a syntactically valid type name that happens not to be found in the catalogs, the result is NULL. The result is -1 if no type modifier is present. to_regtypemod can be combined with to produce appropriate inputs for , allowing a string representing a type name to be canonicalized. format_type(to_regtype('varchar(32)'), to_regtypemod('varchar(32)')) character varying(32) Most of the functions that reconstruct (decompile) database objects have an optional pretty flag, which if true causes the result to be pretty-printed. Pretty-printing suppresses unnecessary parentheses and adds whitespace for legibility. The pretty-printed format is more readable, but the default format is more likely to be interpreted the same way by future versions of PostgreSQL; so avoid using pretty-printed output for dump purposes. Passing false for the pretty parameter yields the same result as omitting the parameter. NameDescription asc Does the column sort in ascending order on a forward scan? desc Does the column sort in descending order on a forward scan? nulls_first Does the column sort with nulls first on a forward scan? nulls_last Does the column sort with nulls last on a forward scan? orderable Does the column possess any defined sort ordering? distance_orderable Can the column be scanned in order by a distance operator, for example ORDER BY col <-> constant ? returnable Can the column value be returned by an index-only scan? search_array Does the column natively support col = ANY(array) searches? search_nulls Does the column support IS NULL and IS NOT NULL searches? NameDescription clusterable Can the index be used in a CLUSTER command? index_scan Does the index support plain (non-bitmap) scans? bitmap_scan Does the index support bitmap scans? backward_scan Can the scan direction be changed in mid-scan (to support FETCH BACKWARD on a cursor without needing materialization)? NameDescription can_order Does the access method support ASC, DESC and related keywords in CREATE INDEX? can_unique Does the access method support unique indexes? can_multi_col Does the access method support indexes with multiple columns? can_exclude Does the access method support exclusion constraints? can_include Does the access method support the INCLUDE clause of CREATE INDEX? FlagDescription EXPLAIN Parameters with this flag are included in EXPLAIN (SETTINGS) commands. NO_SHOW_ALL Parameters with this flag are excluded from SHOW ALL commands. NO_RESET Parameters with this flag do not support RESET commands. NO_RESET_ALL Parameters with this flag are excluded from RESET ALL commands. NOT_IN_SAMPLE Parameters with this flag are not included in postgresql.conf by default. RUNTIME_COMPUTED Parameters with this flag are runtime-computed ones. lists functions related to database object identification and addressing. Function Description pg_get_acl pg_get_acl ( classid oid, objid oid, objsubid integer ) aclitem[] Returns the ACL for a database object, specified by catalog OID, object OID and sub-object ID. This function returns NULL values for undefined objects. pg_describe_object pg_describe_object ( classid oid, objid oid, objsubid integer ) text Returns a textual description of a database object identified by catalog OID, object OID, and sub-object ID (such as a column number within a table; the sub-object ID is zero when referring to a whole object). This description is intended to be human-readable, and might be translated, depending on server configuration. This is especially useful to determine the identity of an object referenced in the pg_depend catalog. This function returns NULL values for undefined objects. pg_identify_object pg_identify_object ( classid oid, objid oid, objsubid integer ) record ( type text, schema text, name text, identity text ) Returns a row containing enough information to uniquely identify the database object specified by catalog OID, object OID and sub-object ID. This information is intended to be machine-readable, and is never translated. type identifies the type of database object; schema is the schema name that the object belongs in, or NULL for object types that do not belong to schemas; name is the name of the object, quoted if necessary, if the name (along with schema name, if pertinent) is sufficient to uniquely identify the object, otherwise NULL; identity is the complete object identity, with the precise format depending on object type, and each name within the format being schema-qualified and quoted as necessary. Undefined objects are identified with NULL values. pg_identify_object_as_address pg_identify_object_as_address ( classid oid, objid oid, objsubid integer ) record ( type text, object_names text[], object_args text[] ) Returns a row containing enough information to uniquely identify the database object specified by catalog OID, object OID and sub-object ID. The returned information is independent of the current server, that is, it could be used to identify an identically named object in another server. type identifies the type of database object; object_names and object_args are text arrays that together form a reference to the object. These three values can be passed to pg_get_object_address to obtain the internal address of the object. pg_get_object_address pg_get_object_address ( type text, object_names text[], object_args text[] ) record ( classid oid, objid oid, objsubid integer ) Returns a row containing enough information to uniquely identify the database object specified by a type code and object name and argument arrays. The returned values are the ones that would be used in system catalogs such as pg_depend; they can be passed to other system functions such as pg_describe_object or pg_identify_object. classid is the OID of the system catalog containing the object; objid is the OID of the object itself, and objsubid is the sub-object ID, or zero if none. This function is the inverse of pg_identify_object_as_address. Undefined objects are identified with NULL values. pg_get_acl is useful for retrieving and inspecting the privileges associated with database objects without looking at specific catalogs. For example, to retrieve all the granted privileges on objects in the current database: postgres=# SELECT (pg_identify_object(s.classid,s.objid,s.objsubid)).*, pg_catalog.pg_get_acl(s.classid,s.objid,s.objsubid) AS acl FROM pg_catalog.pg_shdepend AS s JOIN pg_catalog.pg_database AS d ON d.datname = current_database() AND d.oid = s.dbid JOIN pg_catalog.pg_authid AS a ON a.oid = s.refobjid AND s.refclassid = 'pg_authid'::regclass WHERE s.deptype = 'a'; -[ RECORD 1 ]----------------------------------------- type | table schema | public name | testtab identity | public.testtab acl | {postgres=arwdDxtm/postgres,foo=r/postgres} comment about database objects The functions shown in extract comments previously stored with the command. A null value is returned if no comment could be found for the specified parameters. Function Description col_description col_description ( table oid, column integer ) text Returns the comment for a table column, which is specified by the OID of its table and its column number. (obj_description cannot be used for table columns, since columns do not have OIDs of their own.) obj_description obj_description ( object oid, catalog name ) text Returns the comment for a database object specified by its OID and the name of the containing system catalog. For example, obj_description(123456, 'pg_class') would retrieve the comment for the table with OID 123456. obj_description ( object oid ) text Returns the comment for a database object specified by its OID alone. This is deprecated since there is no guarantee that OIDs are unique across different system catalogs; therefore, the wrong comment might be returned. shobj_description shobj_description ( object oid, catalog name ) text Returns the comment for a shared database object specified by its OID and the name of the containing system catalog. This is just like obj_description except that it is used for retrieving comments on shared objects (that is, databases, roles, and tablespaces). Some system catalogs are global to all databases within each cluster, and the descriptions for objects in them are stored globally as well. The functions shown in can be helpful for checking validity of proposed input data. Function Description Example(s) pg_input_is_valid pg_input_is_valid ( string text, type text ) boolean Tests whether the given string is valid input for the specified data type, returning true or false. This function will only work as desired if the data type's input function has been updated to report invalid input as a soft error. Otherwise, invalid input will abort the transaction, just as if the string had been cast to the type directly. pg_input_is_valid('42', 'integer') t pg_input_is_valid('42000000000', 'integer') f pg_input_is_valid('1234.567', 'numeric(7,4)') f pg_input_error_info pg_input_error_info ( string text, type text ) record ( message text, detail text, hint text, sql_error_code text ) Tests whether the given string is valid input for the specified data type; if not, return the details of the error that would have been thrown. If the input is valid, the results are NULL. The inputs are the same as for pg_input_is_valid. This function will only work as desired if the data type's input function has been updated to report invalid input as a soft error. Otherwise, invalid input will abort the transaction, just as if the string had been cast to the type directly. SELECT * FROM pg_input_error_info('42000000000', 'integer') message | detail | hint | sql_error_code ------------------------------------------------------+--------+------+---------------- value "42000000000" is out of range for type integer | | | 22003 The functions shown in provide server transaction information in an exportable form. The main use of these functions is to determine which transactions were committed between two snapshots. Function Description age age ( xid ) integer Returns the number of transactions between the supplied transaction id and the current transaction counter. mxid_age mxid_age ( xid ) integer Returns the number of multixacts IDs between the supplied multixact ID and the current multixacts counter. pg_current_xact_id pg_current_xact_id () xid8 Returns the current transaction's ID. It will assign a new one if the current transaction does not have one already (because it has not performed any database updates); see for details. If executed in a subtransaction, this will return the top-level transaction ID; see for details. pg_current_xact_id_if_assigned pg_current_xact_id_if_assigned () xid8 Returns the current transaction's ID, or NULL if no ID is assigned yet. (It's best to use this variant if the transaction might otherwise be read-only, to avoid unnecessary consumption of an XID.) If executed in a subtransaction, this will return the top-level transaction ID. pg_xact_status pg_xact_status ( xid8 ) text Reports the commit status of a recent transaction. The result is one of in progress, committed, or aborted, provided that the transaction is recent enough that the system retains the commit status of that transaction. If it is old enough that no references to the transaction survive in the system and the commit status information has been discarded, the result is NULL. Applications might use this function, for example, to determine whether their transaction committed or aborted after the application and database server become disconnected while a COMMIT is in progress. Note that prepared transactions are reported as in progress; applications must check pg_prepared_xacts if they need to determine whether a transaction ID belongs to a prepared transaction. pg_current_snapshot pg_current_snapshot () pg_snapshot Returns a current snapshot, a data structure showing which transaction IDs are now in-progress. Only top-level transaction IDs are included in the snapshot; subtransaction IDs are not shown; see for details. pg_snapshot_xip pg_snapshot_xip ( pg_snapshot ) setof xid8 Returns the set of in-progress transaction IDs contained in a snapshot. pg_snapshot_xmax pg_snapshot_xmax ( pg_snapshot ) xid8 Returns the xmax of a snapshot. pg_snapshot_xmin pg_snapshot_xmin ( pg_snapshot ) xid8 Returns the xmin of a snapshot. pg_visible_in_snapshot pg_visible_in_snapshot ( xid8, pg_snapshot ) boolean Is the given transaction ID visible according to this snapshot (that is, was it completed before the snapshot was taken)? Note that this function will not give the correct answer for a subtransaction ID (subxid); see for details. pg_get_multixact_members pg_get_multixact_members ( multixid xid ) setof record ( xid xid, mode text ) Returns the transaction ID and lock mode for each member of the specified multixact ID. The lock modes forupd, fornokeyupd, sh, and keysh correspond to the row-level locks FOR UPDATE, FOR NO KEY UPDATE, FOR SHARE, and FOR KEY SHARE, respectively, as described in . Two additional modes are specific to multixacts: nokeyupd, used by updates that do not modify key columns, and upd, used by updates or deletes that modify key columns. The internal transaction ID type xid is 32 bits wide and wraps around every 4 billion transactions. However, the functions shown in , except age, mxid_age, and pg_get_multixact_members, use a 64-bit type xid8 that does not wrap around during the life of an installation and can be converted to xid by casting if required; see for details. The data type pg_snapshot stores information about transaction ID visibility at a particular moment in time. Its components are described in . pg_snapshot's textual representation is xmin:xmax:xip_list. For example 10:20:10,14,15 means xmin=10, xmax=20, xip_list=10, 14, 15. Name Description xmin Lowest transaction ID that was still active. All transaction IDs less than xmin are either committed and visible, or rolled back and dead. xmax One past the highest completed transaction ID. All transaction IDs greater than or equal to xmax had not yet completed as of the time of the snapshot, and thus are invisible. xip_list Transactions in progress at the time of the snapshot. A transaction ID that is xmin <= X < xmax and not in this list was already completed at the time of the snapshot, and thus is either visible or dead according to its commit status. This list does not include the transaction IDs of subtransactions (subxids). In releases of PostgreSQL before 13 there was no xid8 type, so variants of these functions were provided that used bigint to represent a 64-bit XID, with a correspondingly distinct snapshot data type txid_snapshot. These older functions have txid in their names. They are still supported for backward compatibility, but may be removed from a future release. See . Function Description txid_current txid_current () bigint See pg_current_xact_id(). txid_current_if_assigned txid_current_if_assigned () bigint See pg_current_xact_id_if_assigned(). txid_current_snapshot txid_current_snapshot () txid_snapshot See pg_current_snapshot(). txid_snapshot_xip txid_snapshot_xip ( txid_snapshot ) setof bigint See pg_snapshot_xip(). txid_snapshot_xmax txid_snapshot_xmax ( txid_snapshot ) bigint See pg_snapshot_xmax(). txid_snapshot_xmin txid_snapshot_xmin ( txid_snapshot ) bigint See pg_snapshot_xmin(). txid_visible_in_snapshot txid_visible_in_snapshot ( bigint, txid_snapshot ) boolean See pg_visible_in_snapshot(). txid_status txid_status ( bigint ) text See pg_xact_status(). The functions shown in provide information about when past transactions were committed. They only provide useful data when the configuration option is enabled, and only for transactions that were committed after it was enabled. Commit timestamp information is routinely removed during vacuum. Function Description pg_xact_commit_timestamp pg_xact_commit_timestamp ( xid ) timestamp with time zone Returns the commit timestamp of a transaction. pg_xact_commit_timestamp_origin pg_xact_commit_timestamp_origin ( xid ) record ( timestamp timestamp with time zone, roident oid) Returns the commit timestamp and replication origin of a transaction. pg_last_committed_xact pg_last_committed_xact () record ( xid xid, timestamp timestamp with time zone, roident oid ) Returns the transaction ID, commit timestamp and replication origin of the latest committed transaction. The functions shown in print information initialized during initdb, such as the catalog version. They also show information about write-ahead logging and checkpoint processing. This information is cluster-wide, not specific to any one database. These functions provide most of the same information, from the same source, as the application. Function Description pg_control_checkpoint pg_control_checkpoint () record Returns information about current checkpoint state, as shown in . pg_control_system pg_control_system () record Returns information about current control file state, as shown in . pg_control_init pg_control_init () record Returns information about cluster initialization state, as shown in . pg_control_recovery pg_control_recovery () record Returns information about recovery state, as shown in . Column Name Data Type checkpoint_lsn pg_lsn redo_lsn pg_lsn redo_wal_file text timeline_id integer prev_timeline_id integer full_page_writes boolean next_xid text next_oid oid next_multixact_id xid next_multi_offset xid oldest_xid xid oldest_xid_dbid oid oldest_active_xid xid oldest_multi_xid xid oldest_multi_dbid oid oldest_commit_ts_xid xid newest_commit_ts_xid xid checkpoint_time timestamp with time zone Column Name Data Type pg_control_version integer catalog_version_no integer system_identifier bigint pg_control_last_modified timestamp with time zone Column Name Data Type max_data_alignment integer database_block_size integer blocks_per_segment integer wal_block_size integer bytes_per_wal_segment integer max_identifier_length integer max_index_columns integer max_toast_chunk_size integer large_object_chunk_size integer float8_pass_by_value boolean data_page_checksum_version integer default_char_signedness boolean Column Name Data Type min_recovery_end_lsn pg_lsn min_recovery_end_timeline integer backup_start_lsn pg_lsn backup_end_lsn pg_lsn end_of_backup_record_required boolean The functions shown in print version information. Function Description version version () text Returns a string describing the PostgreSQL server's version. You can also get this information from , or for a machine-readable version use . Software developers should use server_version_num (available since 8.2) or instead of parsing the text version. unicode_version unicode_version () text Returns a string representing the version of Unicode used by PostgreSQL. icu_unicode_version icu_unicode_version () text Returns a string representing the version of Unicode used by ICU, if the server was built with ICU support; otherwise returns NULL The functions shown in print information about the status of WAL summarization. See . Function Description pg_available_wal_summaries pg_available_wal_summaries () setof record ( tli bigint, start_lsn pg_lsn, end_lsn pg_lsn ) Returns information about the WAL summary files present in the data directory, under pg_wal/summaries. One row will be returned per WAL summary file. Each file summarizes WAL on the indicated TLI within the indicated LSN range. This function might be useful to determine whether enough WAL summaries are present on the server to take an incremental backup based on some prior backup whose start LSN is known. pg_wal_summary_contents pg_wal_summary_contents ( tli bigint, start_lsn pg_lsn, end_lsn pg_lsn ) setof record ( relfilenode oid, reltablespace oid, reldatabase oid, relforknumber smallint, relblocknumber bigint, is_limit_block boolean ) Returns one information about the contents of a single WAL summary file identified by TLI and starting and ending LSNs. Each row with is_limit_block false indicates that the block identified by the remaining output columns was modified by at least one WAL record within the range of records summarized by this file. Each row with is_limit_block true indicates either that (a) the relation fork was truncated to the length given by relblocknumber within the relevant range of WAL records or (b) that the relation fork was created or dropped within the relevant range of WAL records; in such cases, relblocknumber will be zero. pg_get_wal_summarizer_state pg_get_wal_summarizer_state () record ( summarized_tli bigint, summarized_lsn pg_lsn, pending_lsn pg_lsn, summarizer_pid int ) Returns information about the progress of the WAL summarizer. If the WAL summarizer has never run since the instance was started, then summarized_tli and summarized_lsn will be 0 and 0/00000000 respectively; otherwise, they will be the TLI and ending LSN of the last WAL summary file written to disk. If the WAL summarizer is currently running, pending_lsn will be the ending LSN of the last record that it has consumed, which must always be greater than or equal to summarized_lsn; if the WAL summarizer is not running, it will be equal to summarized_lsn. summarizer_pid is the PID of the WAL summarizer process, if it is running, and otherwise NULL. As a special exception, the WAL summarizer will refuse to generate WAL summary files if run on WAL generated under wal_level=minimal, since such summaries would be unsafe to use as the basis for an incremental backup. In this case, the fields above will continue to advance as if summaries were being generated, but nothing will be written to disk. Once the summarizer reaches WAL generated while wal_level was set to replica or higher, it will resume writing summaries to disk.