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. **参考资料** [Object Identifier Types](https://www.postgresql.org/docs/12/datatype-oid.html)