PostgreSQL中將物件oid和物件名相互轉換

kahnyao發表於2024-11-11
SQL物件

PostgreSQL中將物件oid轉為物件名

使用pg的內部資料型別將物件oid轉為物件名，可以簡化一些系統檢視的關聯查詢。

資料庫型別轉換對應型別的oid

可以用以下資料庫型別轉換對應型別的oid（以pg12為例）

postgres=# select typname from pg_type where typname ~ '^reg';
    typname
---------------
 regclass
 regconfig
 regdictionary
 regnamespace
 regoper
 regoperator
 regproc
 regprocedure
 regrole
 regtype
(10 rows)

對應關係

物件名稱 型別 轉換規則
pg_class regclass pg_class.oid::regclass
pg_ts_dict regdictionary pg_ts_dict.oid::regdictionary
pg_namespace regnamespace pg_namespace.oid::regnamespace
pg_operator regoperator pg_operator.oid::regoperator
pg_proc regproc pg_proc.oid::regproc
pg_roles
pg_user		 regrole pg_roles.oid::regrole
pg_user.usesysid::regrole
pg_type regtype pg_type.oid::regtype
以下幾個型別暫不確定用途，待研究：
regprocedure
regoper
regconfig

建立測試資料

psql -U postgres
create user test password 'test';
create database testdb with owner=test;
\c testdb
CREATE SCHEMA AUTHORIZATION test;
psql -U test -d testdb
create table test_t1(id int);
create table test_t2(id int);
create table test_t3(id int);

基於如上測試資料，查詢test模式下有哪些表，以及表的owner

傳統表關聯的方式使用以下SQL，關聯pg_class、pg_namespace、pg_roles/pg_user

psql -U test -d testdb
-- 查詢使用者關聯pg_user查詢
SELECT
  t3.nspname AS SCHEMA,
  t1.relname AS tablename,
  t2.usename AS OWNER 
FROM
  pg_class t1
  JOIN pg_user t2 ON t1.relowner = t2.usesysid
  JOIN pg_namespace t3 ON t1.relnamespace = t3.OID 
WHERE
  t1.relkind = 'r' 
  AND t3.nspname = 'test';

 schema | tablename | owner
--------+-----------+-------
 test   | test_t1   | test
 test   | test_t2   | test
 test   | test_t3   | test
(3 rows)

-- 查詢使用者關聯pg_roles查詢
SELECT
  t3.nspname AS SCHEMA,
  t1.relname AS tablename,
  t2.rolname AS OWNER 
FROM
  pg_class t1
  JOIN pg_roles t2 ON t1.relowner = t2.oid
  JOIN pg_namespace t3 ON t1.relnamespace = t3.OID 
WHERE
  t1.relkind = 'r' 
  AND t3.nspname = 'test';

 schema | tablename | owner
--------+-----------+-------
 test   | test_t1   | test
 test   | test_t2   | test
 test   | test_t3   | test
(3 rows)

如上為了實現查詢效果需要關聯三張表，查詢比較繁瑣，如果使用物件轉換就很簡單了，如下：

psql -U test -d testdb
SELECT
  relnamespace :: REGNAMESPACE AS SCHEMA,
  relname AS tablename,
  relowner :: REGROLE AS OWNER 
FROM
  pg_class 
WHERE
  relnamespace :: REGNAMESPACE :: TEXT = 'test' 
  AND relkind = 'r';

 schema | tablename | owner
--------+-----------+-------
 test   | test_t1   | test
 test   | test_t2   | test
 test   | test_t3   | test
(3 rows)

將物件名轉為oid型別

轉換關係

物件型別 轉換規則
table '表名'::regclass::oid
function/procedure '函式名/儲存過程名'::regproc::oid
schema '模式名'::regnamespace::oid
user/role '使用者名稱/角色名'::regrole::oid
type '型別名稱'::regtype::oid

測試示例

錶轉換

drop table if exists test_t;
create table test_t(id int);

postgres=# select oid from pg_class where relname = 'test_t';
  oid
-------
 16508
(1 row)

postgres=# select 'test_t'::regclass::oid;
  oid
-------
 16508
(1 row)

函式轉換

CREATE OR REPLACE FUNCTION test_fun(
    arg1 INTEGER,
    arg2 INTEGER,
    arg3 TEXT
)
RETURNS INTEGER
AS $$
BEGIN
    RETURN arg1 + arg2;
END;
$$ LANGUAGE plpgsql;


postgres=# select oid,proname from pg_proc where proname = 'test_fun';
  oid  | proname
-------+----------
 16399 | test_fun
(1 row)

postgres=# select 'test_fun'::regproc::oid;
  oid
-------
 16399
(1 row)

模式轉換

create schema test_schema;

postgres=# select oid,nspname from pg_namespace where nspname='test_schema';
  oid  |   nspname
-------+-------------
 16511 | test_schema
(1 row)

postgres=# select 'test_schema'::regnamespace::oid;
  oid
-------
 16511
(1 row)

使用者/角色

create user test_user;

postgres=# select usesysid,usename from pg_user where usename='test_user';
 usesysid |  usename
----------+-----------
    16512 | test_user
(1 row)

postgres=# select 'test_user'::regrole::oid;
  oid
-------
 16512
(1 row)

型別

CREATE TYPE type_sex AS ENUM ('male', 'female');

postgres=# select oid,typname from pg_type where typname='type_sex';
  oid  | typname
-------+----------
 16514 | type_sex
(1 row)

postgres=# select 'type_sex'::regtype::oid;
  oid
-------
 16514
(1 row)

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