-- 使用超級用戶安裝
CREATE EXTENSION insert_username;

-- 查看已安裝擴展
SELECT * FROM pg_available_extensions WHERE name = 'insert_username';

-- 查看擴展提供的函數
\df+ insert_username.*

white=# CREATE EXTENSION insert_username;
CREATE EXTENSION
white=# SELECT * FROM pg_available_extensions WHERE name = 'insert_username';
      name       | default_version | installed_version |                  comment                   
-----------------+-----------------+-------------------+--------------------------------------------
 insert_username | 1.0             | 1.0               | functions for tracking who changed a table
(1 row)

white=# \df+ insert_username.*
                                                                           List of functions
 Schema | Name | Result data type | Argument data types | Type | Volatility | Parallel | Owner | Security | Access privileges | Language | Internal name | D
escription 
--------+------+------------------+---------------------+------+------------+----------+-------+----------+-------------------+----------+---------------+--
-----------
(0 rows)

white=# 

-- 創(chuàng)建測試表
CREATE TABLE documents (
    id serial PRIMARY KEY,
    content text,
    created_by text,  -- 記錄創(chuàng)建者
    modified_by text  -- 記錄最后修改者
);

-- 為表添加觸發(fā)器
CREATE TRIGGER track_document_users
BEFORE INSERT OR UPDATE ON documents
FOR EACH ROW EXECUTE FUNCTION insert_username();

white=# CREATE TABLE yewu1.documents (
white(#     id int,
white(#     name varchar(20),
white(#     created_by text,   
white(#     modified_by text   
white(# );
CREATE TABLE
white=# CREATE TRIGGER track_document_users
white-# BEFORE INSERT OR UPDATE ON yewu1.documents
white-# FOR EACH ROW EXECUTE FUNCTION insert_username();
CREATE TRIGGER
white=# 
white=# \d yewu1.documents
                       Table "yewu1.documents"
   Column    |         Type          | Collation | Nullable | Default 
-------------+-----------------------+-----------+----------+---------
 id          | integer               |           |          | 
 name        | character varying(20) |           |          | 
 created_by  | text                  |           |          | 
 modified_by | text                  |           |          | 
Triggers:
    track_document_users BEFORE INSERT OR UPDATE ON yewu1.documents FOR EACH ROW EXECUTE FUNCTION insert_username()

-- 創(chuàng)建使用不同列名的表
CREATE TABLE projects (
    id serial PRIMARY KEY,
    name text,
    creator text,      -- 替代 created_by
    last_editor text   -- 替代 modified_by
);

-- 使用參數指定列名
CREATE TRIGGER track_project_users
BEFORE INSERT OR UPDATE ON projects
FOR EACH ROW EXECUTE FUNCTION insert_username('creator', 'last_editor');

-- 只跟蹤創(chuàng)建者
CREATE TRIGGER track_creator_only
BEFORE INSERT ON projects
FOR EACH ROW EXECUTE FUNCTION insert_username('creator', NULL);

-- 只跟蹤修改者
CREATE TRIGGER track_editor_only
BEFORE UPDATE ON projects
FOR EACH ROW EXECUTE FUNCTION insert_username(NULL, 'last_editor');

-- 對大表考慮禁用觸發(fā)器進行批量操作
ALTER TABLE large_table DISABLE TRIGGER track_large_table_users;

-- 批量更新操作
UPDATE large_table SET ...;

-- 重新啟用觸發(fā)器
ALTER TABLE large_table ENABLE TRIGGER track_large_table_users;

-- 防止手動修改跟蹤列
REVOKE UPDATE ON created_by FROM public;