返回类型：bool

示例：

openGauss=# select pg_check_authid(1);
pg_check_authid
-----------------
(1 row)

返回类型：text

备注：pg_describe_object返回由目录OID，对象OID和一个（或许0个）子对象ID指定的数据库对象的描述。这有助于确认存储在pg_depend系统表中对象的身份。

返回类型：text

返回类型：text

备注：pg_get_constraintdef和pg_get_indexdef分别从约束或索引上使用创建命令进行重构。

返回类型：text

返回类型：text

备注：pg_get_expr反编译一个独立表达式的内部形式，比如一个字段的缺省值。在检查系统表的内容的时候很有用。如果表达式可能包含关键字，则指定他们引用相关的OID作为第二个参数；如果没有关键字，零就足够了。

返回类型：text

openGauss=# 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)

返回类型：text

备注：pg_get_function_arguments返回一个函数的参数列表，需要在CREATE FUNCTION中使用这种格式。

返回类型：text

备注：pg_get_function_identity_arguments返回需要的参数列表用来标识函数，这种形式需要在ALTER FUNCTION中使用，并且这种形式省略了默认值。

返回类型：text

备注：pg_get_function_result为函数返回适当的RETURNS子句。

返回类型：text

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

返回类型：text

openGauss=# CREATE TABLE sales
openGauss-# (prod_id NUMBER(6),
openGauss(#  cust_id NUMBER,
openGauss(#  time_id DATE,
openGauss(#  channel_id CHAR(1),
openGauss(#  promo_id NUMBER(6),
openGauss(#  quantity_sold NUMBER(3),
openGauss(#  amount_sold NUMBER(10,2)
openGauss(# )
PARTITION BY RANGE( time_id) INTERVAL('1 day')
openGauss-# (
openGauss(#  partition p1 VALUES LESS THAN ('2019-02-01 00:00:00'),
openGauss(#  partition p2 VALUES LESS THAN ('2019-02-02 00:00:00')
openGauss(# );
CREATE TABLE
openGauss=# create index index_sales on sales(prod_id) local (PARTITION idx_p1 ,PARTITION idx_p2);
CREATE INDEX
openGauss=# -- 插入数据没有匹配的分区，新创建一个分区，并将数据插入该分区
openGauss=# INSERT INTO sales VALUES(1, 12, '2019-02-05 00:00:00', 'a', 1, 1, 1);
INSERT 0 1
openGauss=# select oid from pg_class where relname = 'index_sales';
-------
 24632
(1 row)
openGauss=# 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)
openGauss=# 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

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

返回类型：text

备注：pg_get_functiondef为函数返回一个完整的CREATE OR REPLACE FUNCTION语句。

返回类型：setof record

备注：pg_get_keywords返回一组关于描述服务器识别SQL关键字的记录。word列包含关键字。catcode列包含一个分类代码：U表示通用的，C表示列名，T表示类型或函数名，或R表示保留。catdesc列包含了一个可能本地化描述分类的字符串。

返回类型：name

备注：pg_get_userbyid通过角色的OID抽取对应的用户名。

返回类型：text

示例：

openGauss=# select pg_check_authid(20);
pg_check_authid
-----------------
(1 row)

返回类型：text

返回类型：text

备注：pg_get_viewdef重构出定义视图的SELECT查询。这些函数大多数都有两种形式，其中带有pretty_bool参数，且参数为true时，是"适合打印"的结果，这种格式更容易读。另一种是缺省的格式，更有可能被将来的不同版本用同样的方法解释。如果是用于转储，那么尽可能避免使用适合打印的格式。给pretty-print参数传递false生成的结果和没有这个参数的变种生成的结果是完全一样。

返回类型：text

返回类型：text

返回类型：text

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

返回类型：text

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

返回类型：text

备注：pg_get_tabledef重构出表定义的CREATE语句，包含了表定义本身、索引信息、comments信息。对于表对象依赖的group、schema、tablespace、server等信息，需要用户自己去创建，表定义里不会有这些对象的创建语句。

返回类型：setof record

备注：pg_options_to_table当通过pg_class.reloptions或pg_attribute.attoptions时返回存储选项名称/值对（option_name/option_value）的集合。

返回类型：setof oid

备注：pg_tablespace_databases允许检查表空间的状况，返回在该表空间中保存了对象的数据库OID集合。如果这个函数返回数据行，则该表空间就是非空的，因此不能删除。要显示该表空间中的特定对象，用户需要连接pg_tablespace_databases标识的数据库与查询pg_class系统表。

返回类型：text

返回类型：regtype

返回类型：text(source text), text(path text), text(target text)

返回类型：text

openGauss=# select * from pg_get_serial_sequence('t1', 'c1');
 pg_get_serial_sequence 
------------------------
 public.serial
(1 row)

返回类型：int16, int16, int16, int16, Boolean

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

注释信息函数

返回类型：text

备注：col_description返回一个表中字段的注释，通过表OID和字段号来声明。

返回类型：text

备注：带有两个参数的obj_description返回一个数据库对象的注释，该对象是通过其OID和其所属的系统表名称声明。比如，obj_description(123456,'pg_class')将返回OID为123456的表的注释。只带一个参数的obj_description只要求对象OID。

obj_description不能用于表字段，因为字段没有自己的OID。

返回类型：text

返回类型：text

备注：shobj_description和obj_description差不多，不同之处仅在于前者用于共享对象。一些系统表是通用于GaussDB中所有数据库的全局表，因此这些表的注释也是全局存储的。

返回类型：bigint

返回类型：bigint

返回类型：txid_snapshot

返回类型：setof bigint

返回类型：bigint

返回类型：bigint

返回类型：Boolean

返回类型：xid, text, timestamptz, oid, oid，text

返回类型：xid, text, timestamptz, name, name，text

返回类型：Boolean

返回值如下：

返回值：hstore

示例：

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

返回值：值数组

示例：

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

返回值：键的集合。

示例：

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

返回类型：SETOF record

返回类型：SETOF record

参数：nan

返回值类型：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

参数：nan

返回值类型：threadid text, tid bigint, thrdtype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

参数：text

返回值类型：real

参数：text

返回值类型：boolean

参数：location text

参数：oid

返回值类型：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

参数：oid

返回值类型：bigint

参数：nan

返回值类型：sessid text, sesstype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

参数：nan

返回值类型：threadid text, tid bigint, thrdtype text, contextname text, level smallint, parent text, totalsize bigint, freesize bigint, usedsize bigint

参数：nan

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

参数：nan

返回值类型：queryid bigint, plan_node_id integer, plan_node_name text, start_time timestamp with time zone, ec_operator integer, ec_status text, ec_execute_datanode text, ec_dsn text, ec_username text, ec_query text, ec_libodbc_type text, ec_fetch_count bigint

参数：nan

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

参数：nan

返回值类型：min_mem_util integer, max_mem_util integer, min_cpu_util integer, max_cpu_util integer, min_io_util integer, max_io_util integer, used_mem_rate integer

参数：pid integer

返回值类型：datid oid, threadid bigint, sessionid bigint, threadpid integer, usesysid oid, appname text, query text, priority bigint, block_time bigint, elapsed_time bigint, total_cpu_time bigint, skew_percent integer, statement_mem integer, active_points integer, dop_value integer, current_cgroup text, current_status text, enqueue_state text, attribute text, is_plana boolean, node_group text, srespool name

参数：nan

返回值类型：queryid bigint, plan_node_id integer, plan_node_name text, start_time timestamp with time zone, duration bigint, tuple_processed bigint, min_peak_memory integer, max_peak_memory integer, average_peak_memory integer, ec_operator integer, ec_status text, ec_execute_datanode text, ec_dsn text, ec_username text, ec_query text, ec_libodbc_type text, ec_fetch_count bigint

参数：nan

返回值类型：instancename text, timestamp timestamp with time zone, used_cpu integer, free_memory integer, used_memory integer, io_await double precision, io_util double precision, disk_read double precision, disk_write double precision, process_read bigint, process_write bigint, logical_read bigint, logical_write bigint, read_counts bigint, write_counts bigint

参数：nan

返回值类型：instancename text, timestamp timestamp with time zone, used_cpu integer, free_memory integer, used_memory integer, io_await double precision, io_util double precision, disk_read double precision, disk_write double precision, process_read bigint, process_write bigint, logical_read bigint, logical_write bigint, read_counts bigint, write_counts bigint

参数：nan

返回值类型：nodename text, threadid bigint, block_time bigint, duration bigint, estimate_total_time bigint, estimate_left_time bigint, schemaname text, query_band text, spill_info text, control_group text, estimate_memory integer, min_peak_memory integer, max_peak_memory integer, average_peak_memory integer, memory_skew_percent integer, min_spill_size integer, max_spill_size integer, average_spill_size integer, spill_skew_percent integer, min_dn_time bigint, max_dn_time bigint, average_dn_time bigint, dntime_skew_percent integer, min_cpu_time bigint, max_cpu_time bigint, total_cpu_time bigint, cpu_skew_percent integer, min_peak_iops integer, max_peak_iops integer, average_peak_iops integer, iops_skew_percent integer, warning text, query text, query_plan text, cpu_top1_node_name text, cpu_top2_node_name text, cpu_top3_node_name text, cpu_top4_node_name text, cpu_top5_node_name text, mem_top1_node_name text, mem_top2_node_name text, mem_top3_node_name text, mem_top4_node_name text, mem_top5_node_name text, cpu_top1_value bigint, cpu_top2_value bigint, cpu_top3_value bigint, cpu_top4_value bigint, cpu_top5_value bigint, mem_top1_value bigint, mem_top2_value bigint, mem_top3_value bigint, mem_top4_value bigint, mem_top5_value bigint, top_mem_dn text, top_cpu_dn text

参数：nan

返回值类型：threadid bigint, maxcurr_iops integer, mincurr_iops integer, maxpeak_iops integer, minpeak_iops integer, iops_limits integer, io_priority integer, curr_io_limits integer

参数：nan

返回值类型：statement text, block_time bigint, elapsed_time bigint, total_cpu_time bigint, qualification_time bigint, skew_percent integer, control_group text, status text, action text