本节介绍了PostgreSQL的OID类型,官方文档的定义是:
Object identifiers (OIDs) are used internally by PostgreSQL as primary keys for various system tables. Type >oid repesents an object identifier.
OID定义为无符号整型数字,PG内置了转换函数从 regproc, regprocedure, regoper, regoperator, regclass, regtype, regrole, regnamespace, regconfig, and regdictionary 这些类型转换为OID.
TODO
下面是一些例子:
查询某张表的属性
[local]:5432 pg12@testdb=# SELECT * FROM pg_attribute
WHERE attrelid = (SELECT oid FROM pg_class WHERE relname = 'tbl') limit 1;
-[ RECORD 1 ]-+---------
attrelid | 32774
attname | tableoid
atttypid | 26
attstattarget | 0
attlen | 4
attnum | -6
attndims | 0
attcacheoff | -1
atttypmod | -1
attbyval | t
attstorage | p
attalign | i
attnotnull | t
atthasdef | f
atthasmissing | f
attidentity |
attgenerated |
attisdropped | f
attislocal | t
attinhcount | 0
attcollation | 0
attacl |
attoptions |
attfdwoptions |
attmissingval |
Time: 5.209 ms
-->
[local]:5432 pg12@testdb=# SELECT * FROM pg_attribute where attrelid = 'tbl'::regclass limit 1;
-[ RECORD 1 ]-+---------
attrelid | 32774
attname | tableoid
atttypid | 26
attstattarget | 0
attlen | 4
attnum | -6
attndims | 0
attcacheoff | -1
atttypmod | -1
attbyval | t
attstorage | p
attalign | i
attnotnull | t
atthasdef | f
atthasmissing | f
attidentity |
attgenerated |
attisdropped | f
attislocal | t
attinhcount | 0
attcollation | 0
attacl |
attoptions |
attfdwoptions |
attmissingval |
Time: 1.205 ms
查询操作符+的相关信息
[local]:5432 pg12@testdb=# select * from pg_operator where oid='+(int,float)'::regoperator;
ERROR: operator does not exist: +(int,float)
LINE 1: select * from pg_operator where oid='+(int,float)'::regopera...
^
Time: 1.502 ms
[local]:5432 pg12@testdb=# select * from pg_operator where oid='+(float,float)'::regoperator;
-[ RECORD 1 ]+---------
oid | 591
oprname | +
oprnamespace | 11
oprowner | 10
oprkind | b
oprcanmerge | f
oprcanhash | f
oprleft | 701
oprright | 701
oprresult | 701
oprcom | 591
oprnegate | 0
oprcode | float8pl
oprrest | -
oprjoin | -
Time: 3.446 ms
注意:操作符需指定参数.