System Information Functions
Session Information Functions
- SYS_CONTEXT()
Description: Returns the value of the parameter associated with the context namespace at the current time.
Return type: text
Example:
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SELECT SYS_CONTEXT('userenv','NLS_CURRENCY'); sys_context ------------- $ (1 row) SELECT SYS_CONTEXT('userenv','NLS_DATE_FORMAT'); sys_context --------------- ISO, MDY (1 row) SELECT SYS_CONTEXT('userenv','NLS_DATE_LANGUAGE'); sys_context ------------- en_US.UTF-8 (1 row)
- current_catalog
Description: Name of the current database (called "catalog" in the SQL standard)
Return type: name
Example:
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testdb=# SELECT current_catalog; current_database ------------------ testdb (1 row)
- current_database()
Description: Name of the current database
Return type: name
Example:
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testdb=# SELECT current_database(); current_database ------------------ testdb (1 row)
- current_query()
Description: Text of the current query execution committed by the client (which might contain more than one statement)
Return type: text
Example:
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gaussdb=# SELECT current_query(); current_query ------------------------- SELECT current_query(); (1 row)
- current_schema[()]
Description: Name of the current schema
Return type: name
Example:
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gaussdb=# SELECT current_schema(); current_schema ---------------- public (1 row)
Note: 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: Name of a schema in the search path
Return type: name[]
Example:
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gaussdb=# SELECT current_schemas(true); current_schemas --------------------- {pg_catalog,public} (1 row)
Note:
current_schemas(Boolean) returns an array of the names of all schemas in the search path. The Boolean option specifies whether implicitly included system schemas such as pg_catalog are included in the returned search path.
The search path can be altered at run time. The command is as follows:
1SET search_path TO schema [, schema, ...]
- database()
Description: Returns the name of the current schema.
Parameter: none
Return type: name
Example:
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gaussdb=# SELECT database(); database ---------- public (1 row)
This function takes effect only when sql_compatibility is set to 'B', b_format_version is set to '5.7', and b_format_dev_version is set to 's1'.
- current_user
Description: Username in the current operating environment.
Return type: name
Example:
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gaussdb=# SELECT current_user; current_user -------------- omm (1 row)
Note: current_user is the user identifier used for permission check. Normally it is equal to the session user, but it can be changed by using SET ROLE. It also changes during the execution of functions with the SECURITY DEFINER attribute.
- definer_current_user
Description: Username in the current operating environment.
Return type: name
Example:
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gaussdb=# SELECT definer_current_user(); definer_current_user ---------------------- omm (1 row)
- pg_current_sessionid()
Description: Session ID in the current operating environment.
Return type: text
Example:
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gaussdb=# 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 operating environment. The structure of the value is Timestamp.Session ID. When enable_thread_pool is set to on, the actual session ID is used. When enable_thread_pool is set to off, the session ID is the thread ID.
- pg_current_sessid
Description: Session ID in the current operating environment.
Return type: text
Example:
gaussdb=# select pg_current_sessid(); pg_current_sessid ------------------- 140308875015936 (1 row)Note: In thread pool mode, the ID of the current session is obtained. In non-thread pool mode, the backend thread ID of the current session is obtained.
- pg_current_userid
Return type: text
gaussdb=# SELECT pg_current_userid(); pg_current_userid ------------------- 10 (1 row) - working_version_num()
Description: Version number. It returns a version number related to system compatibility.
Return type: int
Example:
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gaussdb=# SELECT working_version_num(); working_version_num --------------------- 92231 (1 row)
- tablespace_oid_name(oid)
Description: Queries the tablespace name based on the tablespace OID.
Return type: text
Example:
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gaussdb=# 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.
This function is valid only in remote connection mode.
Return type: inet
Example:
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gaussdb=# 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.
This function is valid only in remote connection mode.
Return type: int
Example:
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gaussdb=# 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 accepts the current connection.
This function is valid only in remote connection mode.
Return type: inet
Example:
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gaussdb=# 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 number of the port receiving the current connection. All these functions return NULL if the current connection is via a UDS.
This function is valid only in remote connection mode.
Return type: int
Example:
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gaussdb=# SELECT inet_server_port(); inet_server_port ------------------ 8000 (1 row)
- pg_backend_pid()
Description: Thread ID of the service thread connected to the current session.
Return type: int
Example:
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gaussdb=# 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 when the server configuration files were last loaded.
Return type: timestamp with time zone
Example:
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gaussdb=# 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:
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gaussdb=# 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 0 if it has no temporary schemas (because no temporary tables are created). 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: Specifies whether the schema is the temporary schema of another session.
Return type: Boolean
Example:
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gaussdb=# SELECT pg_is_other_temp_schema(25356); pg_is_other_temp_schema ------------------------- f (1 row)
- pg_listening_channels()
Description: Name of the channel that the session is currently listening on.
Return type: SETOF text
Example:
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gaussdb=# 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 currently listening on.
- pg_postmaster_start_time()
Description: Server start time. pg_postmaster_start_time returns the timestamp with time zone when the server is started.
Return type: timestamp with time zone
Example:
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gaussdb=# 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 the CREATE RULE command for a rule.
Return type: text
Example:
gaussdb=# 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:
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gaussdb=# SELECT sessionid2pid(sessid::cstring) FROM gs_session_stat LIMIT 2; sessionid2pid ----------------- 139973107902208 139973107902208 (2 rows)
- session_context( 'namespace' , 'parameter')
Description: Obtains and returns the parameter values of a specified namespace.
Return type: VARCHAR
Example:
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gaussdb=# SELECT session_context('USERENV', 'CURRENT_SCHEMA'); session_context ------------------ public (1 row)
Note: Currently, the current_user, current_schema, client_info, ip_address, sessionid, and sid parameters are supported.
- pg_trigger_depth()
Description: Nesting level of triggers.
Return type: int
Example:
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gaussdb=# SELECT pg_trigger_depth(); pg_trigger_depth ------------------ 0 (1 row)
- session_user
Description: Session username.
Return type: name
Example:
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gaussdb=# SELECT session_user; session_user -------------- omm (1 row)
Note: session_user usually specifies the initial user connected to the current database, but the system administrator can change this setting by using SET SESSION AUTHORIZATION.
- user
Description: Equivalent to current_user.
Return type: name
Example:
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gaussdb=# SELECT user; current_user -------------- omm (1 row)
- getpgusername()
Description: Obtains the database username.
Return type: name
Example:
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gaussdb=# SELECT getpgusername(); getpgusername --------------- GaussDB_userna (1 row)
- getdatabaseencoding()
Description: Obtains the database encoding mode.
Return type: name
Example:
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gaussdb=# SELECT getdatabaseencoding(); getdatabaseencoding --------------------- SQL_ASCII (1 row)
- version()
Description: Version information. version returns a string describing a server's version.
Return type: text
Example:
gaussdb=# SELECT version(); version ------------------------------------------------------------------------------------------------------------------------------------------------------------- gaussdb (GaussDB Kernel XXX.X.XXX build fab4f5ea) compiled at 2021-10-24 11:58:22 commit 3086 last mr 6592 release (1 row)
- opengauss_version()
Description: openGauss version information.
Return type: text
The following is an example. Replace x.x.x in the query result with the actual value.
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gaussdb=# SELECT opengauss_version(); opengauss_version ------------------- x.x.x (1 row)
- gs_deployment()
Description: Information about the deployment mode of the current system.
Return type: text
Example:
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gaussdb=# SELECT gs_deployment(); gs_deployment --------------------- BusinessCentralized (1 row)
- get_hostname()
Description: Returns the host name of the current node.
Return type: text
Example:
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gaussdb=# SELECT get_hostname(); get_hostname -------------- linux-user (1 row)
- get_nodename()
Description: Returns the name of the current node.
Return type: text
Example:
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gaussdb=# SELECT get_nodename(); get_nodename -------------- datanode1 (1 row)
- get_nodeinfo(text)
Description: Returns the value of the corresponding node information based on the search attribute. Currently, the search attributes include node_name and node_type.
Return type: text
Example:
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gaussdb=# SELECT get_nodeinfo('node_type'); get_nodeinfo -------------- CEN_DN (1 row) gaussdb=# SELECT get_nodeinfo('node_name'); get_nodeinfo -------------- datanode1 (1 row)
- get_schema_oid(cstring)
Description: Returns the OID of the queried schema.
Return type: oid
Example:
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gaussdb=# SELECT get_schema_oid('public'); get_schema_oid ---------------- 2200 (1 row)
- get_client_info()
Description: Returns client information.
Return type: record
Access Permission Query Functions
Permissions on DDL statements, including ALTER, DROP, COMMENT, INDEX, and VACUUM, are inherent permissions implicitly owned by the owner.
The following access permission query function only specifies whether a user has a certain permission on an object. That is, the permission on the object recorded in the acl column of the system catalog is returned.
- has_any_column_privilege(user, table, privilege)
Description: Queries whether a specified user has permission for any column of a 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: Checks whether the current user has the permission to access any column of a table. For details about the valid parameter types, see Table 1.
Return type: Boolean
Note: 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 those of has_table_privilege, except that the desired access permission type must be some combination of SELECT, INSERT, UPDATE, COMMENT or REFERENCES.
Note that having any of these permissions at the table level indicates that the permission is implicitly granted for each column of the table. Therefore, has_any_column_privilege always returns true if has_table_privilege has the same parameters. A success message is also returned if a column-level permission is granted for at least one column.
- has_column_privilege(user, table, column, privilege)
Description: Specifies whether a specified user has the permission to access columns.
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: Checks whether the current user has the permission to access any column. 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 parameter possibilities are analogous to those of has_table_privilege, with the addition that the column can be specified either by name or attribute number. The desired access permission type must be some combination of SELECT, INSERT, UPDATE, COMMENT or REFERENCES.
Note that having any of these permissions at the table level indicates that the permission is implicitly granted for each column of the table.
- has_cek_privilege(user, cek, privilege)
Description: Specifies whether a specified user has permission for CEKs. The following table describes the parameters.
Table 3 Parameter type description Parameter
Valid Input Parameter Type
Description
Value Range
user
name, oid
A specific user
Username or ID
cek
text, oid
CEK
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: Specifies whether a specified user has permission for CMKs. The following table describes the parameters.
Table 4 Parameter type description Parameter
Valid Input Parameter Type
Description
Value Range
user
name, oid
A specific user
Username or ID
cmk
text, oid
CMK
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: Specifies whether a specified user has permission for databases. The following table describes the parameters.
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: Checks 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 parameter possibilities are analogous to those of 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, directory, privilege)
Description: Specifies whether a specified user has permission for directories.
Table 6 Parameter type description Parameter
Valid Input Parameter Type
user
name, oid
directory
text, oid
privilege
text
Return type: Boolean
- has_directory_privilege(directory, privilege)
Description: Checks whether the current user has the permission to access the directory. For details about the valid parameter types, see Table 6.
Return type: Boolean
- has_foreign_data_wrapper_privilege(user, fdw, privilege)
Description: Specifies whether a specified user has permission for foreign data wrappers.
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: Specifies whether the current user has permission for accessing foreign-data wrappers. For details about the 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 parameter possibilities are analogous to those of has_table_privilege. The desired access permission type must be USAGE.
- has_function_privilege(user, function, privilege)
Description: Specifies whether a specified user has permission for functions.
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: Specifies whether the current user has permissions on functions. Table 8 describes the valid parameter types.
Return type: Boolean
Note: has_function_privilege checks whether a user can access a function in a particular way. Its parameter possibilities are analogous to those of has_table_privilege. When a function is specified by a text string rather than by an 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: Specifies whether a specified user has permission for languages.
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: Specifies whether the current user has permissions on languages. Table 9 describes the valid parameter types.
Return type: Boolean
Note: has_language_privilege checks whether a user can access a procedural language in a particular way. Its parameter possibilities are analogous to those of has_table_privilege. The desired access permission type must be 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. Its parameter possibilities are analogous to those of has_table_privilege. The access permission type must be USAGE, CREATE, COMPUTE, ALTER, or DROP.
Return type: Boolean
- has_schema_privilege(user, schema, privilege)
Description: Specifies whether a specified user has permission for schemas.
Return type: Boolean
- has_schema_privilege(schema, privilege)
Description: Specifies whether the current user has permission for schemas.
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 those of has_table_privilege. The desired access permission type must be a combination among CREATE, USAGE, ALTER, DROP, and COMMENT. If the check type contains the CREATE permission and the checked schema is a schema with the same name as the user, the function returns TRUE only when the user has the owner permission for the schema due to the special constraint of the schema with the same name.
- has_server_privilege(user, server, privilege)
Description: Specifies whether a specified user has permission for foreign servers.
Return type: Boolean
- has_server_privilege(server, privilege)
Description: Specifies whether the current user has permission for foreign servers.
Return type: Boolean
Note: has_server_privilege checks whether a user can access a foreign server in a particular way. Its parameter possibilities are analogous to those of has_table_privilege. The access permission type must be USAGE, ALTER, DROP, or COMMENT.
- has_table_privilege(user, table, privilege)
Description: Specifies whether a specified user has permission for tables.
Return type: Boolean
- has_table_privilege(table, privilege)
Description: Specifies whether the current user has permission for tables.
Return type: Boolean
Note: has_table_privilege checks whether a user can access a table in a particular way. The user can be specified by name or by OID (pg_authid.oid), or be set to public, which indicates public pseudo roles. If this parameter is omitted, current_user is used. The table can be specified by name or by OID. When it is specified 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 the grant option. Also, multiple permission types can be separated by commas (,), in which case the result will be true if any of the listed permissions is held.
Example:
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gaussdb=# SELECT has_table_privilege('tpcds.web_site', 'select'); has_table_privilege --------------------- t (1 row) gaussdb=# 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: Specifies whether a specified user has permission for tablespaces.
Return type: Boolean
- has_tablespace_privilege(tablespace, privilege)
Description: Specifies whether the current user has permission for tablespaces.
Return type: Boolean
Note: has_tablespace_privilege checks whether a user can access a tablespace in a particular way. Its parameter possibilities are analogous to those of has_table_privilege. The access permission type must be CREATE, ALTER, DROP, or COMMENT.
- pg_has_role(user, role, privilege)
Description: Specifies whether a specified user has permission for roles.
Return type: Boolean
- pg_has_role(role, privilege)
Description: Specifies whether the current user has permission for roles.
Return type: Boolean
Note: pg_has_role checks whether a user can access a role in a particular way. Its parameter possibilities are analogous to those of has_table_privilege, except that public cannot be used as a username. The desired access permission type must be some combination of MEMBER or USAGE. MEMBER denotes direct or indirect membership in the role (that is, permission SET ROLE), while USAGE denotes the usage permission on the role that is available without the SET ROLE permission.
- has_any_privilege(user, privilege)
Description: Queries whether a specified user has certain ANY permission. If multiple permissions are queried at the same time, true is returned as long as one permission is obtained.
Return type: Boolean
Table 11 Parameter type description Parameter
Valid Input Parameter Type
Description
Value Range
user
name
A specific user
Existing username
privilege
text
ANY permission
The options are as follows:
- CREATE ANY TABLE [WITH ADMIN OPTION]
- ALTER ANY TABLE [WITH ADMIN OPTION]
- DROP ANY TABLE [WITH ADMIN OPTION]
- SELECT ANY TABLE [WITH ADMIN OPTION]
- INSERT ANY TABLE [WITH ADMIN OPTION]
- UPDATE ANY TABLE [WITH ADMIN OPTION]
- DELETE ANY TABLE [WITH ADMIN OPTION]
- CREATE ANY SEQUENCE [WITH ADMIN OPTION]
- CREATE ANY INDEX [WITH ADMIN OPTION]
- CREATE ANY FUNCTION [WITH ADMIN OPTION]
- EXECUTE ANY FUNCTION [WITH ADMIN OPTION]
- CREATE ANY PACKAGE [WITH ADMIN OPTION]
- EXECUTE ANY PACKAGE [WITH ADMIN OPTION]
- CREATE ANY TYPE [WITH ADMIN OPTION]
Schema Visibility Query Functions
Each function performs the visibility check on one type of database objects. For functions and operators, an object in the search path is visible if there is no object of the same name and parameter data type earlier in the path. For operator classes, both name and associated index access methods are considered.
All these functions require OIDs to identify the objects to be checked. If you want to test an object by name, it is convenient to use the OID alias type (regclass, regtype, regprocedure, regoperator, regconfig, or regdictionary).
For example, a table is said to be visible if the schema where the table is located 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. To list the names of all visible tables, run the following command:
1
|
gaussdb=# SELECT relname FROM pg_class WHERE pg_table_is_visible(oid); |
- pg_collation_is_visible(collation_oid)
Description: Specifies whether the collation is visible in the search path.
Return type: Boolean
- pg_conversion_is_visible(conversion_oid)
Description: Specifies whether the conversion is visible in the search path.
Return type: Boolean
- pg_function_is_visible(function_oid)
Description: Specifies whether the function is visible in the search path.
Return type: Boolean
- pg_opclass_is_visible(opclass_oid)
Description: Specifies whether the operator class is visible in search path.
Return type: Boolean
- pg_operator_is_visible(operator_oid)
Description: Specifies whether the operator is visible in search path.
Return type: Boolean
- pg_opfamily_is_visible(opclass_oid)
Description: Specifies whether the operator family is visible in search path.
Return type: Boolean
- pg_table_is_visible(table_oid)
Description: Specifies whether the table is visible in the search path.
Return type: Boolean
- pg_ts_config_is_visible(config_oid)
Description: Specifies whether the text search configuration is visible in search path.
Return type: Boolean
- pg_ts_dict_is_visible(dict_oid)
Description: Specifies whether the text search dictionary is visible in search path.
Return type: Boolean
- pg_ts_parser_is_visible(parser_oid)
Description: Specifies whether the text search parser is visible in search path.
Return type: Boolean
- pg_ts_template_is_visible(template_oid)
Description: Specifies whether the text search template is visible in search path.
Return type: Boolean
- pg_type_is_visible(type_oid)
Description: Specifies whether the type (or domain) is visible in search path.
Return type: Boolean
System Catalog Information Functions
- format_type(type_oid, typemod)
Description: Obtains the SQL name of a data type.
Return type: text
Note: format_type returns the SQL name of a data type based on the OID of the data type and possible modifiers. If the specific modifier is unknown, pass NULL at the position of the modifier. Modifiers are generally meaningful only for data types with length restrictions. The SQL name returned by format_type contains the length of the data type, which can be calculated by taking sizeof(int32) from actual storage length [actual storage length – sizeof(int32)] in the unit of bytes. 32-bit space is required to store the customized length set by users. Therefore, the actual storage length contains 4 bytes more than the customized length. In the following example, the SQL name returned by format_type is character varying(6), indicating the length of the varchar type is 6 bytes. Therefore, the actual storage length of the varchar type is 10 bytes.
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gaussdb=# SELECT format_type((SELECT oid FROM pg_type WHERE typname='varchar'), 10); format_type ---------------------- character varying(6) (1 row)
- getdistributekey(table_name)
Description: Obtains a distribution key for a hash table. Distribution is not supported in a standalone system and the return value of this function is empty.
- pg_check_authid(role_oid)
Description: Checks whether a role name with given OID exists.
Return type: Boolean
Example:
gaussdb=# SELECT pg_check_authid(1); pg_check_authid ----------------- f (1 row) - pg_describe_object(catalog_id, object_id, object_sub_id)
Description: Obtains the description of a database object.
Return type: text
Note: pg_describe_object returns the description of a database object specified by a catalog OID, an object OID, and a (possibly zero) sub-object ID. This is useful to determine the identity of an object stored in the pg_depend catalog.
- pg_get_constraintdef(constraint_oid)
Description: Obtains definition of a constraint.
Return type: text
- pg_get_constraintdef(constraint_oid, pretty_bool)
Description: Obtains definition of a constraint.
Return type: text
Note: pg_get_constraintdef and pg_get_indexdef respectively reconstruct the creation 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 of a column. This helps to check the content of system catalogs. If the expression might contain keywords, specify the OID of the relationship they refer to as the second parameter; if no keywords are expected, zero is sufficient.
- pg_get_functiondef(func_oid)
Description: Obtains the definition of a function.
Return type: text
Example:gaussdb=# 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: Obtains argument list of function's definition (with default values).
Return type: text
Note: pg_get_function_arguments returns the parameter list of a function, in the form it would need to appear in CREATE FUNCTION.
- pg_get_function_identity_arguments(func_oid)
Description: Obtains the parameter list to identify a function (without default values).
Return type: text
Note: pg_get_function_identity_arguments returns the parameter list required to identify a function, in the form it would need to appear in ALTER FUNCTION. This form omits default values.
- pg_get_function_result(func_oid)
Description: Obtains the RETURNS clause for a function.
Return type: text
Note: pg_get_function_result returns the appropriate RETURNS clause for the function.
- pg_get_indexdef(index_oid)
Description: Obtains the CREATE INDEX command for an index.
Return type: text
Example:gaussdb=# 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, dump_schema_only)
Description: Obtains the CREATE INDEX command for indexes in dump scenarios. For an interval partitioned table that contains a local index, if dump_schema_only is set to true, the returned index creation statement does not contain the local index information of the automatically created partition. If dump_schema_only is set to false, the returned index creation statement contains the local index information of the automatically created partition. For a non-interval partitioned table or an interval partitioned table that does not contain a local index, the value of dump_schema_only does not affect the returned result of the function.
Return type: text
Example:gaussdb=# CREATE TABLE sales (prod_id NUMBER(6), cust_id NUMBER, time_id DATE, channel_id CHAR(1), promo_id NUMBER(6), quantity_sold NUMBER(3), amount_sold NUMBER(10,2)) PARTITION BY RANGE( time_id) INTERVAL('1 day') (partition p1 VALUES LESS THAN ('2019-02-01 00:00:00'), partition p2 VALUES LESS THAN ('2019-02-02 00:00:00') ); CREATE TABLE gaussdb=# CREATE INDEX index_sales ON sales(prod_id) local (PARTITION idx_p1 ,PARTITION idx_p2); CREATE INDEX gaussdb=# -- If the data to be inserted does not match any partition, create a partition and insert the data into the new partition. gaussdb=# INSERT INTO sales VALUES(1, 12, '2019-02-05 00:00:00', 'a', 1, 1, 1); INSERT 0 1 gaussdb=# SELECT oid FROM pg_class WHERE relname = 'index_sales'; oid ------- 24632 (1 row) gaussdb=# SELECT * FROM pg_get_indexdef(24632, true); pg_get_indexdef -------------------------------------------------------------------------------------------------------------------------- CREATE INDEX index_sales ON sales USING btree (prod_id) LOCAL(PARTITION idx_p1, PARTITION idx_p2) TABLESPACE pg_default (1 row) gaussdb=# SELECT * FROM pg_get_indexdef(24632, false); pg_get_indexdef ------------------------------------------------------------------------------------------------------------------------------------ -------------------- CREATE INDEX index_sales ON sales USING btree (prod_id) LOCAL(PARTITION idx_p1, PARTITION idx_p2, PARTITION sys_p1_prod_id_idx) TA BLESPACE pg_default (1 row
- pg_get_indexdef(index_oid, column_no, pretty_bool)
Description: Obtains the CREATE INDEX command for an index, or definition of just one index column when the value of column_no is not zero.
Example:gaussdb=# 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) gaussdb=# 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: Obtains the 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 keywords. 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: Obtains the role name with a 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:
gaussdb=# SELECT pg_check_authid(20); pg_check_authid ----------------- f (1 row) - pg_get_viewdef(view_name)
Description: Obtains the underlying SELECT command for a view.
Return type: text
- pg_get_viewdef(view_name, pretty_bool)
Description: Obtains the underlying SELECT command for a view. Lines with columns are wrapped to 80 columns if pretty_bool is set to true.
Return type: text
Note: pg_get_viewdef reconstructs the SELECT query that defines a view. Most of these functions come in two forms. When the function has the pretty_bool parameter and the value is true, it can optionally "pretty-print" the result. The pretty-printed format is more readable. The other one is the default format which is more likely to be interpreted in the same way by future versions. Avoid using pretty-printed output for dump purposes. Passing false to the pretty-print parameter generates the same result as a variant without this parameter.
- pg_get_viewdef(view_oid)
Description: Obtains the underlying SELECT command for a view.
Return type: text
- pg_get_viewdef(view_oid, pretty_bool)
Description: Obtains the underlying SELECT command for a view. Lines with columns are wrapped to 80 columns if pretty_bool is set to true.
Return type: text
- pg_get_viewdef(view_oid, wrap_column_int)
Description: Obtains the underlying SELECT command for a view. Lines with columns are wrapped to the specified number of columns and printing is implicit.
Return type: text
- pg_get_tabledef(table_oid)
Description: Obtains the definition of a table based on table_oid.
Example:gaussdb=# 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, storage_type=USTORE, segment=off);+ ILM Security Policies: + POLICY "p4" TABLE + ROW STORE COMPRESS ADVANCED ROW AFTER 1 DAYS OF NO MODIFICATION + STATUS: ENABLED DELETED: NO + (1 row)Return type: text
- pg_get_tabledef(table_name)
Description: Obtains a table definition based on table_name.
Example:gaussdb=# 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, storage_type=USTORE, segment=off);+ ILM Security Policies: + POLICY "p4" TABLE + ROW STORE COMPRESS ADVANCED ROW AFTER 1 DAYS OF NO MODIFICATION + STATUS: ENABLED DELETED: NO + (1 row)Return type: text
Note: pg_get_tabledef reconstructs the CREATE statement of the table definition, including the table definition, index information, comments, and ILM policy (if exists). You need to separately 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: Obtains 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 pg_class.reloptions or pg_attribute.attoptions is passed.
- pg_tablespace_databases(tablespace_oid)
Description: Obtains 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 checked. It returns the set of OIDs of databases that have objects stored in the tablespace. If this function returns any rows of data, the tablespace is not empty and cannot be dropped. To display the specific objects in the tablespace, you need to connect to the databases identified by pg_tablespace_databases and query the pg_class system catalogs.
- pg_tablespace_location(tablespace_oid)
Description: Obtains the path in the file system that this tablespace is located in.
Return type: text
- pg_typeof(any)
Description: Obtains 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. It is declared that the return type of this function is regtype, which is an OID alias type (see Object Identifier Types). It is the same as an OID for comparison purposes but displays as a type name.
Example:
1 2 3 4 5 6 7 8 9 10 11
gaussdb=# SELECT pg_typeof(33); pg_typeof ----------- integer (1 row) gaussdb=# SELECT typlen FROM pg_type WHERE oid = pg_typeof(33); typlen -------- 4 (1 row)
- collation for (any)
Description: Obtains the collation of the parameter.
Return type: text
Note: The expression collation for returns the collation of the value that is passed to it.
The value might be quoted and schema-qualified. If no collation is derived for the parameter expression, then a null value is returned. If the argument is not of a collatable data type, then an error is raised.
Example:
1 2 3 4 5
gaussdb=# SELECT collation for (description) FROM pg_description LIMIT 1; pg_collation_for ------------------ "default" (1 row)
- 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:gaussdb=# 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: int16, int16, int16, int16, Boolean
Example:gaussdb=# 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: Obtains the 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: Obtains the 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 system catalog to which it belongs. 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 OID.
obj_description cannot be used for table columns since columns do not have OIDs of their own.
- obj_description(object_oid)
Description: Obtains the comment for a database object.
Return type: text
- shobj_description(object_oid, catalog_name)
Description: Obtains the comment for a shared database object.
Return type: text
Note: shobj_description is used just like obj_description, except that the former is used for shared objects. Some system catalogs are global to all databases in the GaussDB, and the comments for objects in them are stored globally as well.
XIDs and Snapshots
|
Name |
Description |
|---|---|
|
xmin |
Earliest XID (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 greater than or equal to xmin and less than xmax and that is not in this list was already completed at the time of the snapshot, and is either visible or rolled back according to its commit status. The list does not include txids of subtransactions. |
The textual representation of txid_snapshot is xmin:xmax:xip_list.
For example, 10:20:10,14,15 means xmin=10, xmax=20, xip_list=10, 14, 15.
The following functions provide server transaction information in an exportable form. These functions are mainly used to determine which transactions were committed between two snapshots.
- pgxc_is_committed(transaction_id)
Description: Specifies whether the given XID is committed or ignored. NULL indicates the unknown status (it can be running, ready, frozen, or other status).
Return type: Boolean
- pgxc_is_committed(transaction_id, bucketid)
Description: The hash bucket table is not supported in the current version in centralized mode. An error is reported when the function is called.
- txid_current()
Description: Obtains the current XID.
Return type: bigint
- gs_txid_oldestxmin()
Description: Obtains the minimum XID (specified by oldesxmin).
Return type: bigint
- txid_current_snapshot()
Description: Obtains the current snapshot.
Return type: txid_snapshot
- txid_snapshot_xip(txid_snapshot)
Description: Obtains in-progress XIDs in a snapshot.
Return type: setof bigint
- txid_snapshot_xmax(txid_snapshot)
Description: Obtains xmax of snapshots.
Return type: bigint
- txid_snapshot_xmin(txid_snapshot)
Description: Obtains xmin of snapshots.
Return type: bigint
- txid_visible_in_snapshot(bigint, txid_snapshot)
Description: Specifies whether the XID is visible in a snapshot (excluding subtransaction IDs).
Return type: Boolean
- get_local_prepared_xact()
Description: Obtains the two-phase residual transaction information of the current node, including the XID, GID of the two-phase transaction, prepared time, owner OID, database OID, and node name of the current node.
Return type: xid, text, timestamptz, oid, text
- get_remote_prepared_xacts()
Description: Obtains the two-phase residual transaction information of all remote nodes, including the XID, GID of the two-phase transaction, prepared time, owner name, database name, and node name.
Return type: xid, text, timestamptz, 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 the distributed GaussDB environment. If other users call this function, false is returned.
Return type: Boolean
- gs_get_next_xid_csn()
Description: Returns the values of next_xid and next_csn on all nodes globally.
Return value: See Table 13.
- 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_relation_compression_ratio
Description: Queries the compression rate of a table. By default, 1.0 is returned.
Parameter: text
Return type: real
- pg_relation_with_compression
Description: Specifies whether a table is compressed.
Parameter: text
Return type: Boolean
- pg_stat_file_recursive
Description: Lists all files in a path.
Parameter: location text
- pg_shared_memory_detail
Description: Returns usage information about all generated shared memory contexts. For details about each column, see GS_SHARED_MEMORY_DETAIL.
Parameter: nan
Return type: contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint
- get_gtm_lite_status
Description: Returns the backup XID and CSN on the GTM for fault locating. This system function is not supported in GTM-FREE mode or centralized mode.
- 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_session_iostat_info()
Description: Returns the session load I/O information.
Parameter: nan
Return type: threadid bigint, maxcurr_iops integer, mincurr_iops integer, maxpeak_iops integer, minpeak_iops integer, iops_limits integer, io_priority integer, and curr_io_limits integer
- adm_hist_snapshot_func()
Description: Returns information about the snapshot execution time. To access this function, set the enable_wdr_snapshot parameter to on and obtain the permission to access the snapshot schema, snapshot table, and tables_snap_timestamp tables.
Parameter: nan
Return type: snap_id bigint, dbid oid, begin_interval_time timestamp(3), end_interval_time timestamp(3), flush_elapsed interval day(5) to second(1), begin_interval_time_tz timestamp(3) with time zone, end_interval_time_tz timestamp(3) with time zone
- gs_get_current_version()
Description: Returns the current compilation mode based on the current compilation macro. 'P' is returned.
Parameter: nan
Return type: char
- gs_get_kernel_info()
Description: Transaction information on DNs.
Return value: See Table 14.
Table 14 gs_get_kernel_info parameter description Name
Type
Description
node_name
text
Node name.
module
text
Module name, including:
- XACT (transaction module)
- STANDBY (standby module)
- UNDO (undo module)
- HOTPATH (hot patch module)
name
text
Name of the key data in the memory state, including:
- startup_max_xid (maximum XID when a thread is started)
- recent_local_xmin (minimum XID of local active transactions)
- recent_global_xmin (minimum XID of global active transactions)
- standby_xmin (minimum XID of active transactions on the standby node)
- standby_redo_cleanup_xmin (minimum XID of cleanup logs during redo on the standby node)
- standby_redo_cleanup_xmin_lsn (LSN of the minimum XID of cleanup logs during redo on the standby node)
- local_csn_min (minimum CSN of local active transactions)
- replication_slot_xmin (minimum XID of replication slots)
- replication_slot_catalog_xmin (minimum XID of catalog replication slots)
- global_recycle_xid (minimum XID of global undo recycling transactions)
- global_frozen_xid (minimum XID of global frozen transactions)
- recent_xmin (minimum XID of active transactions in the current session)
- next_csn (CSN of the next transaction)
- hotpatch_additional_info (reserved column for hot patches)
- stmt_session_discard_records (data volume discarded by full SQL statements due to full slots supported by the kernel)
- stmt_shm_flush_discard_records (data volume discarded by full SQL statements due to full ringbuf supported by the kernel)
value
text
Value of the key data in the memory state.
Example:
gaussdb=# SELECT * FROM gs_get_kernel_info(); node_name | module | name | value --------------+---------+-------------------------------+--------- datanode1 | XACT | startup_max_xid | 16488 datanode1 | XACT | recent_local_xmin | 15805 datanode1 | XACT | recent_global_xmin | 15805 datanode1 | STANDBY | standby_xmin | 0 datanode1 | STANDBY | standby_redo_cleanup_xmin | 0 datanode1 | STANDBY | standby_redo_cleanup_xmin_lsn | 0/0 datanode1 | XACT | local_csn_min | 6014225 datanode1 | XACT | replication_slot_xmin | 0 datanode1 | XACT | replication_slot_catalog_xmin | 0 datanode1 | UNDO | global_recycle_xid | 15805 datanode1 | XACT | global_frozen_xid | 0 datanode1 | XACT | recent_xmin | 15805 datanode1 | XACT | next_csn | 6014226 datanode1 | HOTPATH | hotpatch_additional_info | datanode1 | FULL_SQL| stmt_session_discard_records | 0 datanode1 | FULL_SQL| stmt_shm_flush_discard_records| 0 (16 row)
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