Hello
http://www.postgres.cz/index.php/PostgreSQL_SQL_Tricks#Fast_compare_variables_NEW_and_OLD_in_trigger.27s_body
regards
Pavel Stehule
2009/7/23 Willy-Bas Loos <willybas@gmail.com>:
> Hi,
>
> My colleage Geard Troost and I found a handy way of comparing OLD and
> NEW in a trigger function.
> Normally this does not work (if anyone can tell me why, that'd be
> great), but once you cast them to text, it does.
>
> Is there anything to say against this, or can i go ahead and recommend
> this to everyone who wants to check if anything changed before doing
> what their update triggers do?
>
> Cheers,
>
> WBL
>
> Here's the code:
>
> drop table test;
> create table test (id integer primary key, value integer);
> insert into test values (1,1);
> insert into test values (2,1);
> insert into test values (3,1);
> insert into test values (4,1);
> insert into test values (5,1);
> insert into test values (6,1);
>
> create or replace function bla() returns trigger as $$
> begin
> IF (NEW::TEXT = OLD::TEXT) THEN raise notice 'changed';
> END IF;
> return NEW;
> end
> $$
> language plpgsql;
>
> CREATE TRIGGER test_bla BEFORE UPDATE
> ON test FOR EACH ROW
> EXECUTE PROCEDURE public.bla();
>
> update test set value =NULL where id= 1;
> update test set value =NULL where id= 1;
>
> --
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> others because you were born in it." -- George Bernard Shaw
>
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