问题描述
我想创建一个触发器,一旦在模式中创建表,它就会被触发。这个触发器应该向新创建的表添加注释,例如:
[0,2pi]
用 CREATE TRIGGER my_trigger
AFTER CREATE ON my_schema
EXECUTE PROCEDURE add_comment;
做一些类似的事情:
add_comment
但是,我似乎只能在表级别添加触发器。我怎样才能实现在纯 Postgres 中向新创建的表添加注释?
解决方法
您需要一个 EVENT TRIGGER
。
首先创建一个函数:
CREATE OR REPLACE FUNCTION trg_create_table_comment() RETURNS event_trigger
LANGUAGE plpgsql AS $$
DECLARE obj record;
BEGIN
SELECT * FROM pg_event_trigger_ddl_commands() INTO obj;
EXECUTE 'COMMENT ON TABLE ' || obj.object_identity || ' IS ''Created by ' || SESSION_USER || ' on ' || NOW() || '''';
END;
$$;
然后将其附加到 EVENT TRIGGER
:
CREATE EVENT TRIGGER trg_create_table ON ddl_command_end
WHEN TAG IN ('CREATE TABLE','CREATE TABLE AS')
EXECUTE PROCEDURE trg_create_table_comment();
创建表后会触发:
CREATE TABLE foo (id int);
SELECT schemaname,tablename,tableowner,description
FROM pg_tables t
LEFT JOIN pg_description d ON d.objoid = t.tablename::regclass::oid
WHERE tablename = 'foo';
schemaname | tablename | tableowner | description
------------+-----------+------------+---------------------------------------------------
public | foo | jones | Created by jones on 2021-04-10 20:22:22.174874+02