Re: Rows are repeating by the trigger function

> On 30 Oct 2016, at 10:31, Kiran <bangalore.kiran@gmail.com> wrote:
>
> Dear Folks,
>
> I have a  table cf_question with 31 rows.
> I want to insert/update another table cf_user_question_link  when cf_question table is inserted/updated with row(s).
> I have written trigger function for this as follows.
>
>
>     CREATE FUNCTION user_question_link() RETURNS trigger AS
>     $user_question_link$
>     begin
>     SET search_path TO monolith;
>      INSERT INTO
>      cf_user_question_link(cf_user_id,cf_question_id)
>      VALUES(NEW.user_id,NEW.cf_question_id);
>     RETURN NEW;
>     end;
>     $user_question_link$
>     LANGUAGE plpgsql
>     COST 100;
>
>
> /* Call the trigger function */
>
>     CREATE TRIGGER insert_user_question_link AFTER INSERT OR UPDATE
>     ON monolith.cf_question
>     FOR EACH ROW EXECUTE PROCEDURE user_question_link();
>
>
> Problem: The cf_user_question_link gets inserted with 94 rows instead of 31 rows. The 31 rows are repeated 3 times
>                  I tried dropping the trigger function and recreating it but with the same 94 rows in the table.
>
> It would be great if any from the forum point to me where I am doing wrong.

I don't think you want that same trigger to fire on UPDATE of cf_question, like you do now.

On UPDATE you have two choices;
- either you need to take changes to those _id columns into account and delete rows that belong to the OLD link and not
tothe NEW one (or do nothing if those stayed the same) 
- or you do nothing (no trigger needed) because in the majority of cases changing FK's is limited to a few power users
atbest and they're supposed to know what they're doing. 

Alban Hertroys
--
If you can't see the forest for the trees,
cut the trees and you'll find there is no forest.