System Information Functions

Session Information Functions

  • current_catalog

    Description: Name of the current database (called “catalog” in the SQL standard)

    Return type: name

    Example:

    postgres=# SELECT current_catalog;
     current_database
    ------------------
     postgres
    (1 row)
    
  • current_database()

    Description: Name of the current database

    Return type: name

    Example:

    postgres=# SELECT current_database();
     current_database
    ------------------
     postgres
    (1 row)
    
  • current_query()

    Description: Text of the currently executing query, as submitted by the client (might contain more than one statement)

    Return type: text

    Example:

    postgres=# SELECT current_query();
          current_query
    -------------------------
     SELECT current_query();
    (1 row)
    
  • current_schema[()]

    Description: Name of current schema

    Return type: name

    Example:

    postgres=# SELECT current_schema();
     current_schema
    ----------------
     public
    (1 row)
    

    Remarks: current_schema returns the first valid schema name in the search path. (If the search path is empty or contains no valid schema name, NULL is returned.) 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(Boolean)

    Description: Names of schemas in search path

    Return type: name[]

    Example:

    postgres=# SELECT current_schemas(true);
       current_schemas
    ---------------------
     {pg_catalog,public}
    (1 row)
    

    Note:

    current_schemas(Boolean) returns an array of the names of all schemas presently in the search path. The Boolean option determines whether implicitly included system schemas such as pg_catalog are included in the returned search path.

    NOTE: The search path can be altered at run time by running the following command:

    SET search_path TO schema [, schema, ...]
    
  • current_user

    Description: User name of current execution context

    Return type: name

    Example:

    postgres=# SELECT current_user;
     current_user
    --------------
     omm
    (1 row)
    

    Note: 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 SET ROLE. It also changes during the execution of functions with the attribute SECURITY DEFINER.

  • definer_current_user

    Description: User name of current execution context

    Return type: name

    Example:

    postgres=# SELECT definer_current_user();
     definer_current_user
    ----------------------
     omm
    (1 row)
    
  • pg_current_sessionid()

    Description: Session ID of current execution context

    Return type: text

    Example:

    postgres=# SELECT pg_current_sessionid();
        pg_current_sessionid
    ----------------------------
     1579228402.140190434944768
    (1 row)
    

    Note: pg_current_sessionid() is used to obtain the session ID in the current execution context. The structure of the value is Timestamp. Session ID. When enable_thread_pool is set to off, the actual session ID is the thread ID.

  • pg_current_sessid

    Description: Session ID of current execution context

    Return type: text

    Example:

    postgres=# select pg_current_sessid();
    pg_current_sessid
    -------------------
    140308875015936
    (1 row)
    

    Note: In thread pool mode, the session ID of the current session is obtained. In non-thread pool mode, the background thread ID of the current session is obtained.

  • pg_current_userid

    Description: Current user ID.

    Return type: text

    postgres=# SELECT pg_current_userid();
    pg_current_userid
    -------------------
    10
    (1 row)
    
  • tablespace_oid_name()

    Description: Queries the tablespace name based on the tablespace OID.

    Return type: text

    Example:

    postgres=# select tablespace_oid_name(1663);
     tablespace_oid_name
    ---------------------
     pg_default
    (1 row)
    
  • inet_client_addr()

    Description: Remote connection address. inet_client_addr returns the IP address of the current client.

    NOTE: It is available only in remote connection mode.

    Return type: inet

    Example:

    postgres=# SELECT inet_client_addr();
     inet_client_addr
    ------------------
     10.10.0.50
    (1 row)
    
  • inet_client_port()

    Description: Remote connection port. And inet_client_port returns the port number of the current client.

    NOTE: It is available only in remote connection mode.

    Return type: int

    Example:

    postgres=# SELECT inet_client_port();
     inet_client_port
    ------------------
                33143
    (1 row)
    
  • inet_server_addr()

    Description: Local connection address. inet_server_addr returns the IP address on which the server accepted the current connection.

    NOTE: It is available only in remote connection mode.

    Return type: inet

    Example:

    postgres=# SELECT inet_server_addr();
     inet_server_addr
    ------------------
     10.10.0.13
    (1 row)
    
  • inet_server_port()

    Description: Local connection port. inet_server_port returns the port number. All these functions return NULL if the current connection is via a Unix-domain socket.

    NOTE: It is available only in remote connection mode.

    Return type: int

    Example:

    postgres=# SELECT inet_server_port();
     inet_server_port
    ------------------
                 8000
    (1 row)
    
  • pg_backend_pid()

    Description: Process ID of the server process attached to the current session

    Return type: int

    Example:

    postgres=# SELECT pg_backend_pid();
     pg_backend_pid
    -----------------
     140229352617744
    (1 row)
    
  • pg_conf_load_time()

    Description: Configures load time. pg_conf_load_time returns the timestamp with time zone when the server configuration files were last loaded.

    Return type: timestamp with time zone

    Example:

    postgres=# SELECT pg_conf_load_time();
          pg_conf_load_time       
    ------------------------------
     2017-09-01 16:05:23.89868+08
    (1 row)
    
  • pg_my_temp_schema()

    Description: OID of the temporary schema of a session. The value is 0 if the OID does not exist.

    Return type: oid

    Example:

    postgres=# SELECT pg_my_temp_schema();
     pg_my_temp_schema 
    -------------------
                     0
    (1 row)
    

    Note: pg_my_temp_schema 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 returns true if the given OID is the OID of another session's temporary schema.

  • pg_is_other_temp_schema(oid)

    Description: Whether the schema is the temporary schema of another session.

    Return type: Boolean

    Example:

    postgres=# SELECT pg_is_other_temp_schema(25356);
     pg_is_other_temp_schema
    -------------------------
     f
    (1 row)
    
  • pg_listening_channels()

    Description: Channel names that the session is currently listening on

    Return type: SETOF text

    Example:

    postgres=# SELECT pg_listening_channels();
     pg_listening_channels
    -----------------------
    (0 rows)
    

    Note: pg_listening_channels returns a set of names of channels that the current session is listening to.

  • pg_postmaster_start_time()

    Description: Server start time pg_postmaster_start_time returns the timestamp with time zone when the server started.

    Return type: timestamp with time zone

    Example:

    postgres=# SELECT pg_postmaster_start_time();
       pg_postmaster_start_time   
    ------------------------------
     2017-08-30 16:02:54.99854+08
    (1 row)
    
  • pg_get_ruledef(rule_oid)

    Description: Obtains CREATE RULE command for rule.

    Return type: text

    Example:

    postgres=# select * from pg_get_ruledef(24828);
                                    pg_get_ruledef
    -------------------------------------------------------------------
     CREATE RULE t1_ins AS ON INSERT TO t1 DO INSTEAD INSERT INTO t2 (id) VALUES (new.id);
    (1 row)
    
  • sessionid2pid()

    Description: Obtains PID information from a session ID (for example, the sessid column in gs_session_stat).

    Return type: int8

    Example:

    postgres=# select sessionid2pid(sessid::cstring) from gs_session_stat limit 2;
      sessionid2pid
    -----------------
     139973107902208
     139973107902208
    (2 rows)
    
  • pg_trigger_depth()

    Description: Current nesting level of triggers

    Return type: int

    Example:

    postgres=# SELECT pg_trigger_depth();
     pg_trigger_depth 
    ------------------
                    0
    (1 row)
    
  • session_user

    Description: Session user name

    Return type: name

    Example:

    postgres=# SELECT session_user;
     session_user
    --------------
     omm
    (1 row)
    

    Note: session_user is usually the user who initiated the current database connection, but administrators can change this setting with SET SESSION AUTHORIZATION.

  • user

    Description: Equivalent to current_user.

    Return type: name

    Example:

    postgres=# SELECT user;
     current_user
    --------------
     omm
    (1 row)
    
  • getpgusername()

    Description: Obtains the database username.

    Return type: name

    Example:

    postgres=# select getpgusername();
     getpgusername 
    ---------------
     GaussDB_userna
    (1 row)
    
  • getdatabaseencoding()

    Description: Obtains the database encoding mode.

    Return type: name

    Example:

    postgres=# select getdatabaseencoding();
     getdatabaseencoding 
    ---------------------
     SQL_ASCII
    (1 row)
    
  • version()

    Description: version information. version returns a string describing a server's version.

    Return type: text

    Example:

    postgres=# SELECT version();
                                                                    version                                                                
    ---------------------------------------------------------------------------------------------------------------------------------------
     PostgreSQL 9.2.4 (openGauss-1.1.0 build 66e54e4d) compiled at 2020-01-02 13:02:26 commit 7218 last mr 10175  on x86_64-unknown-linux-gnu, compiled by g++ (GCC) 8.2.0, 64-bit
    
    (1 row)
    
  • get_hostname()

    Description: Returns the hostname of the current node.

    Return type: text

    Example:

    postgres=# SELECT get_hostname();
     get_hostname
    --------------
     linux-user
    (1 row)
    
  • get_nodename()

    Description: Returns the name of the current node.

    Return type: text

    Example:

    postgres=# SELECT get_nodename();
     get_nodename
    --------------
     datanode1
    (1 row)
    
  • get_schema_oid(cstring)

    Description: Returns the OID of the queried schema.

    Return type: oid

    Example:

    postgres=# SELECT get_schema_oid('public');
     get_schema_oid
    ----------------
               2200
    (1 row)
    

Access privilege inquiry function

  • has_any_column_privilege(user, table, privilege)

    Description: Queries whether a specified user has permission for any column of table.

    Table 1 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    table

    text, oid

    privilege

    text

    Return type: Boolean

  • has_any_column_privilege(table, privilege)

    Description: Queries whether the current user has permission to access any column of table. For details about the valid parameter types, see Table 1.

    Return type: Boolean

    has_any_column_privilege checks whether a user can access any column of a table in a particular way. Its parameter possibilities are analogous to has_table_privilege, except that the desired access permission type must be some combination of SELECT, INSERT, UPDATE, COMMENT or REFERENCES.

    NOTE: Note that having any of these permissions at the table level implicitly grants it for each column of the table, so has_any_column_privilege will always return true if has_table_privilege does for the same parameters. But has_any_column_privilege also succeeds if there is a column-level grant of the permission for at least one column.

  • has_column_privilege(user, table, column, privilege)

    Description: Queries whether a specified user has permission for column.

    Table 2 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    table

    text, oid

    column

    text, smallint

    privilege

    text

    Return type: Boolean

  • has_column_privilege(table, column, privilege)

    Description: Queries whether the current user has permission to access columns. For details about the valid parameter types, see Table 2.

    Return type: Boolean

    has_column_privilege checks whether a user can access a column in a particular way. Its argument possibilities are analogous to has_table_privilege, with the addition that the column can be specified either by name or attribute number. The desired access permission type must evaluate to some combination of SELECT, INSERT, UPDATE, COMMENT or REFERENCES.

    NOTE: Note that having any of these permissions at the table level implicitly grants it for each column of the table.

  • has_cek_privilege(user, cek, privilege)

    Description: Queries whether a specified user has permission for column encryption key (CEK). The parameters are described as follows:

    Table 3 Parameter type description

    Parameter

    Valid Input Parameter Type

    Description

    Range

    user

    name, oid

    User

    User name or ID

    cek

    text, oid

    Column encryption key

    Name or ID of a CEK.

    privilege

    text

    Permission

    • USAGE: allows users to use the specified CEK.
    • DROP: allows users to delete the specified CEK.

    Return type: Boolean

  • has_cmk_privilege(user, cmk, privilege)

    Description: Queries whether a specified user has permission for client master key (CMK). The parameters are described as follows:

    Table 4 Parameter type description

    Parameter

    Valid Input Parameter Type

    Description

    Range

    user

    name, oid

    User

    User name or ID

    cmk

    text, oid

    Client master key

    Name or ID of the CMK

    privilege

    text

    Permission

    • USAGE: allows users to use the specified CMK.
    • DROP: allows users to delete the specified CMK.

    Return type: Boolean

  • has_database_privilege(user, database, privilege)

    Description: Queries whether a specified user has permission for database. The parameters are described as follows:

    Table 5 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    database

    text, oid

    privilege

    text

    Return type: Boolean

  • has_database_privilege(database, privilege)

    Description: Queries whether the current user has permission to access a database. For details about the valid parameter types, see Table 5.

    Return type: Boolean

    Note: has_database_privilege checks whether a user can access a database in a particular way. Its argument possibilities are analogous to has_table_privilege. The desired access permission type must be some combination of CREATE, CONNECT, TEMPORARY, ALTER, DROP, COMMENT or TEMP (which is equivalent to TEMPORARY).

  • has_directory_privilege(user, database, privilege)

    Description: Queries whether a specified user has permission for directory.

    Table 6 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    database

    text, oid

    privilege

    text

    Return type: Boolean

  • has_directory_privilege(database, privilege)

    Description: Queries whether the current user has permission to access a directory. For details about the valid parameter types, see Table 6.

    Return type: Boolean

  • has_foreign_data_wrapper_privilege(user, fdw, privilege)

    Description: Queries whether a specified user has permission for foreign-data wrapper.

    Table 7 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    fdw

    text, oid

    privilege

    text

    Return type: Boolean

  • has_foreign_data_wrapper_privilege(fdw, privilege)

    Description: Queries whether the current user has permission for foreign-data wrapper. For details about valid parameter types, see Table 7.

    Return type: Boolean

    Note: has_foreign_data_wrapper_privilege checks whether a user can access a foreign-data wrapper in a particular way. Its argument possibilities are analogous to has_table_privilege. The desired access permission type must evaluate to USAGE.

  • has_function_privilege(user, function, privilege)

    Description: Queries whether a specified user has permission for function.

    Table 8 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    function

    text, oid

    privilege

    text

    Return type: Boolean

  • has_function_privilege(function, privilege)

    Description: Queries whether the current user has permission for function. For details about valid parameter types, see Table 8.

    Return type: Boolean

    Note: has_function_privilege checks whether a user can access a function in a particular way. Its argument possibilities are analogous to has_table_privilege. When a function is specified by a text string rather than by OID, the allowed input is the same as that for the regprocedure data type (see Object Identifier Types). The access permission type must be EXECUTE, ALTER, DROP, or COMMENT.

  • has_language_privilege(user, language, privilege)

    Description: Queries whether a specified user has permission for language.

    Table 9 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    language

    text, oid

    privilege

    text

    Return type: Boolean

  • has_language_privilege(language, privilege)

    Description: Queries whether the current user has permission for language. For details about valid parameter types, see Table 9.

    Return type: Boolean

    Note: has_language_privilege checks whether a user can access a procedural language in a particular way. Its argument possibilities are analogous to has_table_privilege. The desired access permission type must evaluate to USAGE.

  • has_nodegroup_privilege(user, nodegroup, privilege)

    Description: Checks whether a user has permission to access a database node.

    Return type: Boolean

    Table 10 Parameter type description

    Parameter

    Valid Input Parameter Type

    user

    name, oid

    nodegroup

    text, oid

    privilege

    text

  • has_nodegroup_privilege(nodegroup, privilege)

    Description: Checks whether a user has permission to access a database node. The parameter is similar to has_table_privilege. The access permission type must be USAGE, CREATE, COMPUTE, ALTER, or CROP.

    Return type: Boolean

  • has_schema_privilege(user, schema, privilege)

    Description: Queries whether a specified user has permission for schema.

    Return type: Boolean

  • has_schema_privilege(schema, privilege)

    Description: Queries whether the current user has permission for schema.

    Return type: Boolean

    Note: has_schema_privilege checks whether a user can access a schema in a particular way. Its parameter possibilities are analogous to has_table_privilege. The desired access permission type must be some combination of CREATE, USAGE, ALTER, DROP or COMMENT.

  • has_server_privilege(user, server, privilege)

    Description: Queries whether a specified user has permission for foreign server.

    Return type: Boolean

  • has_server_privilege(server, privilege)

    Description: Queries whether the current user has permission for foreign server.

    Return type: Boolean

    Note: has_server_privilege checks whether a user can access a foreign server in a particular way. Its argument possibilities are analogous to has_table_privilege. The access permission type must be USAGE, ALTER, DROP, or COMMENT.

  • has_table_privilege(user, table, privilege)

    Description: Queries whether a specified user has permission for table.

    Return type: Boolean

  • has_table_privilege(table, privilege)

    Description: Queries whether the current user has permission for table.

    Return type: Boolean

    has_table_privilege checks whether a user can access a table in a particular way. The user can be specified by name, by OID (pg_authid.oid), public to indicate the PUBLIC pseudo-role, or if the argument is omitted current_user is assumed. The table can be specified by name or by OID. When specifying by name, the name can be schema-qualified if necessary. The desired access permission type is specified by a text string, which must be one of the values SELECT, INSERT, UPDATE, DELETE, TRUNCATE, REFERENCES, TRIGGER, ALTER, DROP, COMMENT, INDEX or VACUUM. Optionally, WITH GRANT OPTION can be added to a permission type to test whether the permission is held with grant option. Also, multiple permission types can be listed separated by commas, in which case the result will be true if any of the listed permissions is held.

    Example:

    postgres=# SELECT has_table_privilege('tpcds.web_site', 'select');
     has_table_privilege  
    --------------------- 
     t 
    (1 row)
    
    postgres=# SELECT has_table_privilege('omm', 'tpcds.web_site', 'select,INSERT WITH GRANT OPTION ');
     has_table_privilege  
    --------------------- 
     t 
    (1 row) 
    
  • has_tablespace_privilege(user, tablespace, privilege)

    Description: Queries whether a specified user has permission for tablespace.

    Return type: Boolean

  • has_tablespace_privilege(tablespace, privilege)

    Description: Queries whether the current user has permission for tablespace.

    Return type: Boolean

    Note: has_tablespace_privilege checks whether a user can access a tablespace in a particular way. Its argument possibilities are analogous to has_table_privilege. The access permission type must be CREATE, ALTER, DROP, or COMMENT.

  • pg_has_role(user, role, privilege)

    Description: Queries whether a specified user has permission for role.

    Return type: Boolean

  • pg_has_role(role, privilege)

    Description: Specifies whether the current user has permission for role.

    Return type: Boolean

    Note: pg_has_role checks whether a user can access a role in a particular way. Its argument possibilities are analogous to has_table_privilege, except that public is not allowed as a user name. The desired access permission type must evaluate to some combination of MEMBER or USAGE. MEMBER denotes direct or indirect membership in the role (that is, the right to do SET ROLE), while USAGE denotes the permissions of the role are available without doing SET ROLE.

Schema Visibility Inquiry Functions

Each function performs the visibility check for one type of database object. For functions and operators, an object in the search path is visible if there is no object of the same name and argument data type(s) earlier in the path. For operator classes, both name and associated index access method are considered.

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, 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. For example, to list the names of all visible tables:

postgres=# SELECT relname FROM pg_class WHERE pg_table_is_visible(oid);
  • pg_collation_is_visible(collation_oid)

    Description: Queries whether the collation is visible in search path.

    Return type: Boolean

  • pg_conversion_is_visible(conversion_oid)

    Description: Queries whether the conversion is visible in search path.

    Return type: Boolean

  • pg_function_is_visible(function_oid)

    Description: Queries whether the function is visible in search path.

    Return type: Boolean

  • pg_opclass_is_visible(opclass_oid)

    Description: Queries whether the operator class is visible in search path.

    Return type: Boolean

  • pg_operator_is_visible(operator_oid)

    Description: Queries whether the operator is visible in search path.

    Return type: Boolean

  • pg_opfamily_is_visible(opclass_oid)

    Description: Queries whether the operator family is visible in search path.

    Return type: Boolean

  • pg_table_is_visible(table_oid)

    Description: Queries whether the table is visible in search path.

    Return type: Boolean

  • pg_ts_config_is_visible(config_oid)

    Description: Queries whether the text search configuration is visible in search path.

    Return type: Boolean

  • pg_ts_dict_is_visible(dict_oid)

    Description: Queries whether the text search dictionary is visible in search path.

    Return type: Boolean

  • pg_ts_parser_is_visible(parser_oid)

    Description: Queries whether the text search parser is visible in search path.

    Return type: Boolean

  • pg_ts_template_is_visible(template_oid)

    Description: Queries whether the text search template is visible in search path.

    Return type: Boolean

  • pg_type_is_visible(type_oid)

    Description: Queries whether the type (or domain) is visible in search path.

    Return type: Boolean

System Catalog Information Functions

  • format_type(type_oid, typemod)

    Description: Gets SQL name of a data type.

    Return type: text

    Note: format_type returns the SQL name of 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. Certain type modifiers are passed for data types with length limitations. The SQL name returned from format_type contains the length of the data type, which can be calculated by taking sizeof(int32) from actual storage length [actual storage len - sizeof(int32)] in the unit of bytes. 32-bit space is required to store the customized length set by users. So the actual storage length contains 4 bytes more than the customized length. In the following example, the SQL name returned from format_type is character varying(6), indicating the length of varchar type is 6 bytes. So the actual storage length of varchar type is 10 bytes.

    postgres=# SELECT format_type((SELECT oid FROM pg_type WHERE typname='varchar'), 10);
         format_type      
    ----------------------
     character varying(6)
    (1 row)
    
  • pg_check_authid(role_oid)

    Description: Check whether a role name with given OID exists.

    Return type: bool

    Example:

    postgres=# select pg_check_authid(1);
    pg_check_authid
    -----------------
    f
    (1 row)
    
  • pg_describe_object(catalog_id, object_id, object_sub_id)

    Description: Gets description of a database object.

    Return type: text

    Note: pg_describe_object returns a description of a database object specified by catalog OID, object OID and a (possibly zero) sub-object ID. This is useful to determine the identity of an object as stored in the pg_depend catalog.

  • pg_get_constraintdef(constraint_oid)

    Description: Gets definition of a constraint.

    Return type: text

  • pg_get_constraintdef(constraint_oid, pretty_bool)

    Description: Gets definition of a constraint.

    Return type: text

    Note: pg_get_constraintdef and pg_get_indexdef respectively reconstruct the creating command for a constraint and an index.

  • pg_get_expr(pg_node_tree, relation_oid)

    Description: Decompiles internal form of an expression, assuming that any Vars in it refer to the relationship indicated by the second parameter.

    Return type: text

  • pg_get_expr(pg_node_tree, relation_oid, pretty_bool)

    Description: Decompiles internal form of an expression, assuming that any Vars in it refer to the relationship indicated by the second parameter.

    Return type: text

    Note: pg_get_expr decompiles the internal form of an individual expression, such as the default value for a column. It can be useful when examining the contents of system catalogs. If the expression might contain Vars, specify the OID of the relationship they refer to as the second parameter; if no Vars are expected, zero is sufficient.

  • pg_get_functiondef(func_oid)

    Description: Gets definition of a function.

    Return type: text

    Example:

    postgres=# select * from pg_get_functiondef(598);
     headerlines |                     definition                     
    -------------+----------------------------------------------------
               4 | CREATE OR REPLACE FUNCTION pg_catalog.abbrev(inet)+
                 |  RETURNS text                                     +
                 |  LANGUAGE internal                                +
                 |  IMMUTABLE STRICT NOT FENCED NOT SHIPPABLE        +
                 | AS $function$inet_abbrev$function$                +
                 | 
    (1 row)
    
  • pg_get_function_arguments(func_oid)

    Description: Gets argument list of function's definition (with default values).

    Return type: text

    Note: pg_get_function_arguments returns the argument list of a function, in the form it would need to appear in within CREATE FUNCTION.

  • pg_get_function_identity_arguments(func_oid)

    Description: Gets argument list to identify a function (without default values).

    Return type: text

    Note: pg_get_function_identity_arguments returns the argument list necessary to identify a function, in the form it would need to appear in within ALTER FUNCTION. This form omits default values.

  • pg_get_function_result(func_oid)

    Description: Gets RETURNS clause for function.

    Return type: text

    Note: pg_get_function_result returns the appropriate RETURNS clause for the function.

  • pg_get_indexdef(index_oid)

    Description: Gets CREATE INDEX command for index.

    Return type: text

    Example:

    postgres=# select * from pg_get_indexdef(16416);
                                 pg_get_indexdef                             
    -------------------------------------------------------------------------
     CREATE INDEX test3_b_idx ON test3 USING btree (b) TABLESPACE pg_default
    (1 row)
    
  • pg_get_indexdef(index_oid, column_no, pretty_bool)

    Description: Gets CREATE INDEX command for index, or definition of just one index column when column_no is not zero.

    Example:

    postgres=# select * from pg_get_indexdef(16416, 0, false);
                                 pg_get_indexdef                             
    -------------------------------------------------------------------------
     CREATE INDEX test3_b_idx ON test3 USING btree (b) TABLESPACE pg_default
    (1 row)
    postgres=# select * from pg_get_indexdef(16416, 1, false);
     pg_get_indexdef 
    -----------------
     b
    (1 row)
    

    Return type: text

    Note: pg_get_functiondef returns a complete CREATE OR REPLACE FUNCTION statement for a function.

  • pg_get_keywords()

    Description: Gets list of SQL keywords and their categories.

    Return type: SETOF record

    Note: pg_get_keywords 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 unreserved, C for column name, T for type or function name, or R for reserved. The catdesc column contains a possibly-localized string describing the category.

  • pg_get_userbyid(role_oid)

    Description: Gets role name with given OID.

    Return type: name

    Note: pg_get_userbyid extracts a role's name given its OID.

  • pg_check_authid(role_id)

    Description: Checks whether a user exists based on role_id.

    Return type: text

    Example:

    postgres=# select pg_check_authid(20);
    pg_check_authid
    -----------------
    f
    (1 row)
    
  • pg_get_viewdef(view_name)

    Description: Gets underlying SELECT command for view.

    Return type: text

  • pg_get_viewdef(view_name, pretty_bool)

    Description: Gets underlying SELECT command for view, lines with columns are wrapped to 80 columns if pretty_bool is true.

    Return type: text

    Note: pg_get_viewdef reconstructs the SELECT query that defines a view. Most of these functions come in two variants. When the function has the parameter pretty_bool and the value is true, it can optionally “pretty-print” the result. The pretty-printed format is more readable. The other one is default format which is more likely to be interpreted the same way by future versions of PostgreSQL. Avoid using pretty-printed output for dump purposes. Passing false for the pretty-print parameter yields the same result as the variant that does not have the parameter at all.

  • pg_get_viewdef(view_oid)

    Description: Gets underlying SELECT command for view.

    Return type: text

  • pg_get_viewdef(view_oid, pretty_bool)

    Description: Gets underlying SELECT command for view, lines with columns are wrapped to 80 columns if pretty_bool is true.

    Return type: text

  • pg_get_viewdef(view_oid, wrap_column_int)

    Description: Gets underlying SELECT command for view, wrapping lines with columns as specified, printing is implied.

    Return type: text

  • pg_get_tabledef(table_oid)

    Description: Obtains a table definition based on table_oid.

    Example:

    postgres=# select * from pg_get_tabledef(16384);
                        pg_get_tabledef                    
    -------------------------------------------------------
     SET search_path = public;                            +
     CREATE  TABLE t1 (                                   +
             c1 bigint DEFAULT nextval('serial'::regclass)+
     )                                                    +
     WITH (orientation=row, compression=no)               +
     TO GROUP group1;
    (1 row)
    

    Return type: text

  • pg_get_tabledef(table_name)

    Description: Obtains a table definition based on table_name.

    Example:

    postgres=# select * from pg_get_tabledef('t1');
                        pg_get_tabledef                    
    -------------------------------------------------------
     SET search_path = public;                            +
     CREATE  TABLE t1 (                                   +
             c1 bigint DEFAULT nextval('serial'::regclass)+
     )                                                    +
     WITH (orientation=row, compression=no)               +
     TO GROUP group1;
    (1 row)
    

    Return type: text

    Remarks: pg_get_tabledef reconstructs the CREATE statement of the table definition, including the table definition, index information, and comments. Users need to create the dependent objects of the table, such as groups, schemas, tablespaces, and servers. The table definition does not include the statements for creating these dependent objects.

  • pg_options_to_table(reloptions)

    Description: Gets the set of storage option name/value pairs.

    Return type: SETOF record

    Note: pg_options_to_table returns the set of storage option name/value pairs (option_name/option_value) when passed pg_class.reloptions or pg_attribute.attoptions.

  • pg_tablespace_databases(tablespace_oid)

    Description: Gets the set of database OIDs that have objects in the specified tablespace.

    Return type: SETOF oid

    Note: pg_tablespace_databases allows a tablespace to be examined. It returns the set of OIDs of databases that have objects stored in the tablespace. If this function returns any rows, the tablespace is not empty and cannot be dropped. To display the specific objects populating the tablespace, you will need to connect to the databases identified by pg_tablespace_databases and query their pg_class catalogs.

  • pg_tablespace_location(tablespace_oid)

    Description: Gets the path in the file system that this tablespace is located in.

    Return type: text

  • pg_typeof(any)

    Description: Gets the data type of any value.

    Return type: regtype

    Note: pg_typeof 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 Object Identifier Types). This means that it is the same as an OID for comparison purposes but displays as a type name.

    Example:

    postgres=# SELECT pg_typeof(33);
     pg_typeof 
    -----------
     integer
    (1 row)
    
    postgres=# SELECT typlen FROM pg_type WHERE oid = pg_typeof(33);
     typlen 
    --------
          4
    (1 row)
    
  • collation for (any)

    Description: Gets the collation of the parameter.

    Return type: text

    Note: The expression collation for returns the collation of the value that is passed to it.

    Example:

    postgres=# SELECT collation for (description) FROM pg_description LIMIT 1;
     pg_collation_for 
    ------------------
     "default"
    (1 row)
    

    The value might be quoted and schema-qualified. If no collation is derived for the argument expression, then a null value is returned. If the parameter is not of a collectable data type, then an error is thrown.

  • pg_extension_update_paths(name)

    Description: Returns the version update path of the specified extension.

    Return type: text(source text), text(path text), text(target text)

  • pg_get_serial_sequence(tablename, colname)

    Description: Obtains the sequence of the corresponding table name and column name.

    Return type: text

    Example:

    postgres=# select * from pg_get_serial_sequence('t1', 'c1');
     pg_get_serial_sequence 
    ------------------------
     public.serial
    (1 row)
    
  • pg_sequence_parameters(sequence_oid)

    Description: Obtains the parameters of a specified sequence, including the start value, minimum value, maximum value, and incremental value.

    Return type: bigint, bigint, bigint, bigint, Boolean

    Example:

    postgres=# select * from pg_sequence_parameters(16420);
     start_value | minimum_value |    maximum_value    | increment | cycle_option 
    -------------+---------------+---------------------+-----------+--------------
             101 |             1 | 9223372036854775807 |         1 | f
    (1 row)
    

Comment Information Functions

  • col_description(table_oid, column_number)

    Description: Gets comment for a table column.

    Return type: text

    Note: col_description returns the comment for a table column, which is specified by the OID of its table and its column number.

  • obj_description(object_oid, catalog_name)

    Description: Gets comment for a database object.

    Return type: text

    Note: The two-parameter form of obj_description 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. The one-parameter form of obj_description requires only the object OID.

    obj_description cannot be used for table columns since columns do not have OIDs of their own.

  • obj_description(object_oid)

    Description: Gets comment for a database object.

    Return type: text

  • shobj_description(object_oid, catalog_name)

    Description: Gets comment for a shared database object.

    Return type: text

    Note: shobj_description is used just like obj_description except the former is used for retrieving comments on shared objects. Some system catalogs are global to all databases in openGauss, and the comments for objects in them are stored globally as well.

Transaction IDs and Snapshots

The following functions provide server transaction information in an exportable form. The main use of these functions is to determine which transactions were committed between two snapshots.

  • txid_current()

    Description: Gets current transaction ID.

    Return type: bigint

  • txid_current_snapshot()

    Description: Gets current snapshot.

    Return type: txid_snapshot

  • txid_snapshot_xip(txid_snapshot)

    Description: Gets in-progress transaction IDs in snapshot.

    Return type: SETOF bigint

  • txid_snapshot_xmax(txid_snapshot)

    Description: Gets xmax of snapshot.

    Return type: bigint

  • txid_snapshot_xmin(txid_snapshot)

    Description: Gets xmin of snapshot.

    Return type: bigint

  • txid_visible_in_snapshot(bigint, txid_snapshot)

    Description: Queries whether the transaction ID is visible in snapshot. (do not use with subtransaction ids)

    Return type: Boolean

  • get_local_prepared_xact()

    Description: Obtains the two-phase residual transaction information of the current node, including the transaction ID, GID the two-phase transaction, prepared time, owner OID, database OID, and node name of the current node.

    Return type: xid, text, timestamptz, oid, oid, text

  • get_remote_prepared_xacts()

    Description: Obtains the two-phase residual transaction information of all remote nodes, including the transaction ID, GID the two-phase transaction, prepared time, owner name, database name, and node name.

    Return type: xid, text, timestamptz, name, name, text

  • global_clean_prepared_xacts(text, text)

    Description: Concurrently cleans two-phase residual transactions. Only the gs_clean tool can call this function for the cleaning. In other situations, false is returned.

    Return type: Boolean

    The internal transaction ID type (xid) is 64 bits wide and wraps around every 4 billion transactions. txid_snapshot, the data type used by these functions, stores information about transaction ID visibility at a particular moment in time. Table 11 describes its components.

    Table 11 Snapshot components

    Name

    Description

    xmin

    Earliest transaction ID (txid) that is still active. All earlier transactions will either be committed and visible, or rolled back.

    xmax

    First as-yet-unassigned txid. All txids greater than or equal to this are not yet started as of the time of the snapshot, so they are invisible.

    xip_list

    Active txids at the time of the snapshot. The list includes only those active txids between xmin and xmax; there might be active txids higher than xmax. A txid that is xmin <= txid < xmax and not in this list was already completed at the time of the snapshot, and is either visible or dead according to its commit status. The list does not include txids of subtransactions.

    txid_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.

  • slice(hstore, text[])

    Description: Extracts the subset of the hstore type.

    Return type: hstore

    Example:

    postgres=# select slice('a=>1,b=>2,c=>3'::hstore, ARRAY['b','c','x']);
           slice
    --------------------
     "b"=>"2", "c"=>"3"
    (1 row)
    
  • slice_array(hstore, text[])

    Description: Extracts the set of hstore values.

    Return type: value array

    Example:

    postgres=# select slice_array('a=>1,b=>2,c=>3'::hstore, ARRAY['b','c','x']);
     slice_array
    -------------
     {2,3,NULL}
    (1 row)
    
  • skeys(hstore)

    Description: Returns a set of all keys of the hstore type.

    Return type: a set of keys

    Example:

    postgres=# select skeys('a=>1,b=>2');
     skeys
    -------
     a
     b
    (2 rows)
    
  • pg_control_system()

    Description: Returns the status of the system control file.

    Return type: SETOF record

  • pg_control_checkpoint()

    Description: Returns the system checkpoint status.

    Return type: SETOF record

  • pv_builtin_functions

    Description: Displays information about all built-in system functions.

    Parameter: nan

    Return type: proname name, pronamespace oid, proowner oid, prolang oid, procost real, prorows real, provariadic oid, protransform regproc, proisagg boolean, proiswindow boolean, prosecdef boolean, proleakproof boolean, proisstrict boolean, proretset boolean, provolatile “char”, pronargs smallint, pronargdefaults smallint, prorettype oid, proargtypes oidvector, proallargtypes integer[], proargmodes “char”[], proargnames text[], proargdefaults pg_node_tree, prosrc text, probin text, proconfig text[], proacl aclitem[], prodefaultargpos int2vector, fencedmode boolean, proshippable boolean, propackage boolean, oid oid

  • pv_thread_memory_detail

    Description: Returns the memory information of each thread.

    Parameter: nan

    Return type: threadid text, tid bigint, thrdtype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

  • pg_shared_memory_detail

    Description: Returns usage information about all generated shared memory contexts. For details about each column, see SHARED_MEMORY_DETAIL.

    Parameter: nan

    Return type: contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

  • gs_stat_get_wlm_plan_operator_info

    Description: Obtains operator plan information from the internal hash table.

    Parameter: oid

    Return type: datname text, queryid int8, plan_node_id int4, startup_time int8, total_time int8, actual_rows int8, max_peak_memory int4, query_dop int4, parent_node_id int4, left_child_id int4, right_child_id int4, operation text, orientation text, strategy text, options text, condition text, projection text

  • pg_stat_get_partition_tuples_hot_updated

    Description: Returns statistics on the number of hot-updated tuples in a partition with a specified partition ID.

    Parameter: oid

    Return type: bigint

  • gs_session_memory_detail_tp

    Description: Returns the memory usage of the session. For details, see gs_session_memory_detail.

    Parameter: nan

    Return type: sessid text, sesstype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

  • gs_thread_memory_detail

    Description: Returns the memory information of each thread.

    Parameter: nan

    Return type: threadid text, tid bigint, thrdtype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

  • pg_stat_get_wlm_realtime_operator_info

    Description: Obtains the operator information of the real-time execution plan from the internal hash table.

    Parameter: nan

    Return type: queryid bigint, pid bigint, plan_node_id integer, plan_node_name text, start_time timestamp with time zone, duration bigint, status text, query_dop integer, estimated_rows bigint, tuple_processed bigint, min_peak_memory integer, max_peak_memory integer, average_peak_memory integer, memory_skew_percent integer, min_spill_size integer, max_spill_size integer, average_spill_size integer, spill_skew_percent integer, min_cpu_time bigint, max_cpu_time bigint, total_cpu_time bigint, cpu_skew_percent integer, warning text

  • pg_stat_get_wlm_realtime_ec_operator_info

    Description: Obtains the operator information of the EC execution plan from the internal hash table.

    Parameter: nan

    Return type: queryid bigint, plan_node_id integer, plan_node_name text, start_time timestamp with time zone, ec_operator integer, ec_status text, ec_execute_datanode text, ec_dsn text, ec_username text, ec_query text, ec_libodbc_type text, ec_fetch_count bigint

  • pg_stat_get_wlm_operator_info

    Description: Obtains the operator information of the execution plan from the internal hash table.

    Parameter: nan

    Return type: queryid bigint, pid bigint, plan_node_id integer, plan_node_name text, start_time timestamp with time zone, duration bigint, query_dop integer, estimated_rows bigint, tuple_processed bigint, min_peak_memory integer, max_peak_memory integer, average_peak_memory integer, memory_skew_percent integer, min_spill_size integer, max_spill_size integer, average_spill_size integer, spill_skew_percent integer, min_cpu_time bigint, max_cpu_time bigint, total_cpu_time bigint, cpu_skew_percent integer, warning text

  • pg_stat_get_wlm_node_resource_info

    Description: Obtains the resource information of the current node.

    Parameter: nan

    Return type: min_mem_util integer, max_mem_util integer, min_cpu_util integer, max_cpu_util integer, min_io_util integer, max_io_util integer, used_mem_rate integer

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