PostgreSQL：更新视图的触发器不起作用

Question

我正在尝试使更新视图的触发器起作用。如果我正在做并插入它就可以了！但是当我尝试进行 UPDATE 时，它只是不运行。

CREATE OR REPLACE FUNCTION test_trigger_function()
RETURNS trigger AS
$$
    BEGIN
        RAISE NOTICE 'hi';
        RETURN NEW;
    END;
$$ LANGUAGE PLPGSQL;

CREATE TRIGGER test_trigger
INSTEAD OF INSERT OR UPDATE
    ON specific_view
        FOR EACH ROW
            EXECUTE PROCEDURE test_trigger_function();

然后在另一个地方我执行它：

RAISE NOTICE 'before';
UPDATE specific_view SET gender='randomstuff';
RAISE NOTICE 'after';

结果：

psql:test_function.pgsql:134: NOTICE:  before
psql:test_function.pgsql:134: NOTICE:  after

---

插入时：

RAISE NOTICE 'before';
INSERT INTO specific_view (gender)
    VALUES ('randomstuff');
RAISE NOTICE 'after';

返回：

psql:test_function.pgsql:134: NOTICE:  before
psql:test_function.pgsql:134: NOTICE:  hi
CONTEXT:  SQL statement "INSERT INTO specific_view (gender)
                VALUES ('randomstuff')"
PL/pgSQL function ... blahblahblah ... line 261 at SQL statement
psql:test_function.pgsql:134: NOTICE:  after

Answer 1

因为更新触发器在每行被更新时调用一次，所以如果没有行要被更新，它根本不会被调用。

你自己看：

create table test(i int);
create view test_view as select i from test;

CREATE OR REPLACE FUNCTION test_trigger_function()
RETURNS trigger AS
$$
    BEGIN
        RAISE NOTICE 'hi';
        RETURN NEW;
    END;
$$ LANGUAGE PLPGSQL;

CREATE TRIGGER test_trigger
INSTEAD OF INSERT OR UPDATE
    ON test_view
        FOR EACH ROW
            EXECUTE PROCEDURE test_trigger_function();

insert into test_view(i) values(1);            

SELECT * FROM TEST;
SELECT * FROM test_view;

UPDATE test_view set i=1;
-- trigger did not fire

insert into test(i) values(1);  

UPDATE test_view set i=3;
-- trigger fired

SELECT * FROM test_view;