Re: Preventing Deletions with triggers

Jeff Post <POSTJL(at)milwaukee(dot)k12(dot)wi(dot)us> writes:
> CREATE or replace FUNCTION person_fake_delete() RETURNS TRIGGER AS '
> BEGIN
> OLD.status := 1; -- This does the fake deletion
> RETURN NULL; -- I thought this would prevent the delete from
> actually happening.
> END;
> ' LANGUAGE 'plpgsql';

> create trigger person_fake_delete
> before delete on person
> for each row EXECUTE PROCEDURE
> person_fake_delete();

> This however does not work. the tupple is still deleted from the
> table. Any Ideas?

It works for me, in the sense that returning NULL prevents the
deletion. However that assignment to OLD is a no-op: you can't change
the tuple that way. You'd have to do something like

UPDATE person SET status = 1 WHERE key = OLD.key;

("key" being whatever your primary key for the table is)

regards, tom lane