v1.1

System Information Functions

Session Information Functions

current_catalog

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

Return type: name

Example:
```
mogdb=# SELECT current_catalog;
 current_database
------------------
 mogdb
(1 row)
```

current_database()

Description: Name of the current database

Return type: name

Example:

mogdb=# SELECT current_database();
 current_database
------------------
 mogdb
(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:
```
mogdb=# SELECT current_query();
      current_query
-------------------------
 SELECT current_query();
(1 row)
```
current_schema[()]

Description: Name of current schema

Return type: name

Example:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:

mogdb=# SELECT definer_current_user();
 definer_current_user
----------------------
 omm
(1 row)

pg_current_sessionid()

Description: Session ID of current execution context

Return type: text

Example:
```
mogdb=# 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:
```
mogdb=# 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

mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# SELECT inet_server_port();
 inet_server_port
------------------
             8000
(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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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:
```
mogdb=# 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 of a rule.

Return type: text

Example:

mogdb=# 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 pv_session_stat).

Return type: int8

Example:

mogdb=# select sessionid2pid(sessid::cstring) from pv_session_stat limit 2;
  sessionid2pid
-----------------
 139973107902208
 139973107902208
(2 rows)

pg_trigger_depth()

Description: Current nesting level of triggers

Return type: int

Example:

mogdb=# SELECT pg_trigger_depth();
 pg_trigger_depth
------------------
                0
(1 row)

pgxc_version()

Description: Postgres-XC version information

Return type: text

Example:

mogdb=# SELECT pgxc_version();
                                                pgxc_version
-------------------------------------------------------------------------------------------------------------
 Postgres-XC 1.1 on x86_64-unknown-linux-gnu, based on PostgreSQL 9.2.4, compiled by g++ (GCC) 5.4.0, 64-bit
(1 row)

session_user

Description: Session user name

Return type: name

Example:
```
mogdb=# 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:

mogdb=# SELECT user;
 current_user
--------------
 omm
(1 row)

get_shard_oids_byname

Description: Returns the OID of the node when the node name is entered.

Return type: oid

Example:

mogdb=# select get_shard_oids_byname('datanode1');
 get_shard_oids_byname
-----------------------
 {16385}
(1 row)

getpgusername()

Description: Obtains the database username.

Return type: name

Example:

mogdb=# select getpgusername();
 getpgusername
---------------
 MogDB_userna
(1 row)

getdatabaseencoding()

Description: Obtains the database encoding mode.

Return type: name

Example:

mogdb=# select getdatabaseencoding();
 getdatabaseencoding
---------------------
 SQL_ASCII
(1 row)

version()

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

Return type: text

Example:

mogdb=# SELECT version();
                                                                version
---------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.2.4 (MogDB-1.1.0 build 5be05d82) 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:
```
mogdb=# SELECT get_hostname();
 get_hostname
--------------
 linux-user
(1 row)
```
get_nodename()

Description: Returns the name of the current node.

Return type: text

Example:
```
mogdb=# SELECT get_nodename();
 get_nodename
--------------
 coordinator1
(1 row)
```

get_schema_oid(cstring)

Description: Returns the OID of the queried schema.

Return type: oid

Example:

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

pgxc_prepared_xact()

Description: Returns the list of transaction GIDs at the prepared stage in the cluster.

Return type: SETOF text

Example:
```
mogdb=# SELECT pgxc_prepared_xact();
 pgxc_prepared_xact
--------------------
(0 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](#table 1 parameter type).

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, 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](#table 2 parameter type).

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, or REFERENCES.

NOTE:

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

Parameter	Valid Input Parameter Type
user	name, oid
table	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
table	text, oid
column	text, smallint
privilege	text

has_cek_privilege(user, cek, privilege)

Description: Queries whether a specified user has permission for CEK. For details about the valid parameter types, see [Table 3](#table 3 parameter type).

Table 3 Parameter type description

Parameter	Valid Input Parameter Type	Description	Value Range
user	name, oid	User	User name or ID
cek	text, oid	CEK	CEK name or ID
privilege	text	Permission	Usage: A specified CEK is allowed to be used. DROP: A specified CEK is allowed to be deleted.

Return type: Boolean

has_cmk_privilege(user, cmk, privilege)

Description: Queries whether a specified user has permission for CMK. For details about the valid parameter types, see [Table 4](#table 4 parameter type).

Table 4 Parameter type description

Parameter	Valid Input Parameter Type	Description	Value Range
user	name，oid	User	User name or ID
cmk	text，oid	CMK	CMK name or ID
privilege	text	Permission	Usage: A specified CMK is allowed to be used. DROP: A specified CMK is allowed to be deleted.

Return type: Boolean

has_database_privilege(user, database, privilege)

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

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](#table 5 parameter type).

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 evaluate to some combination of CREATE, CONNECT, TEMPORARY, 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](#table 6 parameter type).

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](#table 7 parameter type).

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](#table 8 parameter type).

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 desired access permission type must evaluate to EXECUTE.
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](#table 9 parameter type).

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 cluster 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 cluster node.

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 argument possibilities are analogous to has_table_privilege. The desired access permission type must evaluate to some combination of CREATE or USAGE.
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 desired access permission type must evaluate to USAGE.
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, or TRIGGER. 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:
```
mogdb=# SELECT has_table_privilege('tpcds.web_site', 'select');
 has_table_privilege
---------------------
 t
(1 row)

mogdb=# 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 desired access permission type must evaluate to CREATE.
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.

Parameter	Valid Input Parameter Type
user	name, oid
database	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
database	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
fdw	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
function	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
language	text, oid
privilege	text

Parameter	Valid Input Parameter Type
user	name, oid
nodegroup	text, oid
privilege	text

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:

mogdb=# 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.
```
mogdb=# 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:
```
mogdb=# 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:

mogdb=# 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:

mogdb=# 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:

mogdb=# 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)
mogdb=# select * from pg_get_indexdef(16416, 1, false);
 pg_get_indexdef
-----------------
 b
(1 row)

Return type: text

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:
```
mogdb=# 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:

mogdb=# 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)               +
 DISTRIBUTE BY HASH(c1)                               +
 TO GROUP group1;
(1 row)

Return type: text

pg_get_tabledef(table_name)

Description: Obtains a table definition based on table_name.

Example:

mogdb=# 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)               +
 DISTRIBUTE BY HASH(c1)                               +
 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:
```
mogdb=# SELECT pg_typeof(33);
 pg_typeof
-----------
 integer
(1 row)

mogdb=# 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:
```
mogdb=# 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.
getdistributekey(table_name)

Description: Obtains a distribution key for a hash table.

Return type: text

Example:
```
mogdb=# SELECT getdistributekey('item');
 getdistributekey
------------------
 i_item_sk
(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:
```
mogdb=# 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:

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

pgxc_get_variable_info()

Description: Obtains variable values on the node, including nodeName, nextOid, nextXid, oldestXid, xidVacLimit, oldestXidDB, lastExtendCSNLogpage, startExtendCSNLogpage, nextCommitSeqNo, latestCompleteXid, and startupMaxXid.

Return type: set of pg_variable_info

Example:

mogdb=# select pgxc_get_variable_info( );
                      pgxc_get_variable_info
-------------------------------------------------------------------------
(dn_6004_6005_6006,25617,141396349,2073,20000002073,15808,138111,0,127154152,141396348,104433004)
(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 MogDB, 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.

pgxc_is_committed(transaction_id)

Description: Determines whether the given XID is committed or ignored. NULL indicates the unknown status (such as running, preparing, and freezing).

Return type: bool
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 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

pgxc_stat_get_wal_senders_status()

Description: Returns the reception status of the standby node for node transaction logs.

After the command is executed, the following result is output:

Table 11 pgxc_stat_get_wal_senders_status output parameters

Column	Description
nodename	Name of the primary node
source_ip	IP address of the primary node
source_port	Port of the primary node
dest_ip	IP address of the standby node
dest_port	Port of the standby node
sender_pid	PID of the sending thread
local_role	Type of the primary node
peer_role	Type of the standby node
peer_state	Status of the standby node
state	WAL sender status
sender_sent_location	Sending position of the primary node
sender_write_location	Writing position of the primary node
sender_replay_location	Redo position of the primary node
receiver_received_location	Receiving position of the standby node
receiver_write_location	Writing position of the standby node
receiver_flush_location	Flushing location of the standby node
receiver_replay_location	Redo location of the standby node

The internal transaction ID type (xid) is 32 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 12 describes its components.

Table 12 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:

mogdb=# 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:

mogdb=# 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:
```
mogdb=# select skeys('a=>1,b=>2');
 skeys
-------
 a
 b
(2 rows)
```
simsearch_lib_load_status()

Description: Queries the dynamic library loading status (success or failure).

Return type: SETOF record
simsearch_gpu_vector_status()

Description: Queries whether there is a vector in the status of searchlet.

Return type: SETOF record
pg_control_system()

Description: Returns the system control file status.

Return type: SETOF record
pg_control_checkpoint()

Description: Returns the system checkpoint status.

Return type: SETOF record

Issue