Re: How to avoid (stop) a endless loop in a trigger

On Thu, 2004-03-04 at 14:54, Rodrigo Sakai wrote:
> Hi people, i have a problem here.
> I'm doing a trigger that when a update occurs i need to do an update on the same table (target table), but as known, it causes a endless loop whithin infinit updates. So I need to stop the trigger after it does the first update, is there any way?????
> I tried to do a return null, but that was a very bad idea because it stops completly the function fired by a trigger and all its computation is in vain...
>
> The test trigger that i did is like :
>
> CREATE OR REPLACE FUNCTION public.sp_teste_loop() RETURNS trigger AS '
> begin
> raise notice \'Trigger Fired\';
> if (TG_OP = \'INSERT\') then
> update teste_trigger
> set flg_bool = \'S\'
> where codigo=NEW.codigo;
>
> RETURN NEW;
>
> elsif (TG_OP = \'UPDATE\') then
> update teste_trigger
> set flg_bool = \'N\'
> where codigo=NEW.codigo;
>
> RETURN NULL;
> end if;
> end;
> ' LANGUAGE 'plpgsql' VOLATILE;

Does this update other records, or only the one you are inserting or
updating?

If the former, add " AND flg_bool IS NULL OR flg_bool != \'S\'" to the
update condition (!=\'N\' for the update case); then records that are
already OK will not be touched, so the recursion will stop
automatically.

If the latter, just change NEW.flg_bool and return NEW

> CREATE TRIGGER tr_sp_teste_trigger
> BEFORE INSERT OR UPDATE
> ON public.teste_trigger
> FOR EACH ROW
> EXECUTE PROCEDURE public.sp_teste_loop();
>
> Thank for any help and regards!!!!
>
>
> =====================
> Rodrigo Sakai
> Database Programmer
> rodrigo(at)2bfree(dot)com(dot)br
> http://www.2bfree.com.br
> Tel: (55) (11) 5083-5577
> Fax: (55) (11) 5549-3598
> =====================
>
>
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