Thread: 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.

On 10/30/2016 02:31 AM, Kiran 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();

In addition to what Alban said:

What do you want the trigger function to do ?

In other words what are the condition(s) that are supposed to create a
new row in cf_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

Well actually 1 row + (3 * 31 rows).

So what is the query you are sending to cf_question?

>                  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.
>
> regards
> Kiran


--
Adrian Klaver
adrian.klaver@aklaver.com

On 10/31/2016 02:06 AM, Kiran wrote:
> Hi Adrian,
>
> I want the trigger function to insert a row  in cf_user_question_link
> table with fields as show in the function once the there is a insert
> from in the cf_question table.

If so and I think this was mentioned before, why the UPDATE in the
trigger statement?

>
>
> I know 94 = 1 + (3 * 31).
> I am just having a normal insert statement into cf_question table.

Are there any other triggers on the tables?

>
> regards
> Kiran
>
> On Sun, Oct 30, 2016 at 3:01 PM, Adrian Klaver
> <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> wrote:
>
>     On 10/30/2016 02:31 AM, Kiran 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();
>
>
>     In addition to what Alban said:
>
>     What do you want the trigger function to do ?
>
>     In other words what are the condition(s) that are supposed to create
>     a new row in cf_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
>
>
>     Well actually 1 row + (3 * 31 rows).
>
>     So what is the query you are sending to cf_question?
>
>
>                          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.
>
>         regards
>         Kiran
>
>
>
>     --
>     Adrian Klaver
>     adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
>
>


--
Adrian Klaver
adrian.klaver@aklaver.com

On 31 October 2016 at 14:41, Adrian Klaver <adrian.klaver@aklaver.com> wrote:
> On 10/31/2016 02:06 AM, Kiran wrote:
>> I know 94 = 1 + (3 * 31).
>> I am just having a normal insert statement into cf_question table.
>
> Are there any other triggers on the tables?

I'm fairly confident that the duplicates are from updates on the
cf_question table. Since the trigger also fires on update and then
inserts another record, that would explain the duplication pretty
well.

Nevertheless, if there are other triggers those bear investigation.
--
If you can't see the forest for the trees,
Cut the trees and you'll see there is no forest.

On 10/31/2016 10:02 AM, Kiran wrote:
> Dear Adrian and Alban,
>
> Thanks for the suggestions.
> I revisited the entire tables, triggers related to the tables. I did not
> find anything strange.
> But, I removed all the rows from the* *cf_user_question_link and
> inserted relevant rows into the table from *cf_question*.
>
>
> Also, I recreated the function without the update and deployed it.
> Now the trigger function works as expected ( when a new row is inserted
> into the *cf_question*, a row with necessary fields is inserted into
> the cf_user_question_link table)
>
> Though now the trigger function works as expected but the issue that I
> faced was it because there were rows already in the cf_question table
> before the trigger function was deployed ?

Not really, the issue, as Alban pointed out, was you had UPDATE in the
trigger statement. So every time you  did an UPDATE to cf_question you
got an INSERT into cf_user_question_link. So I suspect somewhere/somehow
you did 3 UPDATES to all the rows in cf_question while you had the old
trigger statement deployed.

>
> regards
> Kiran
>
>
>
>
> On Mon, Oct 31, 2016 at 3:45 PM, Alban Hertroys <haramrae@gmail.com
> <mailto:haramrae@gmail.com>> wrote:
>
>     On 31 October 2016 at 14:41, Adrian Klaver
>     <adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>> wrote:
>     > On 10/31/2016 02:06 AM, Kiran wrote:
>     >> I know 94 = 1 + (3 * 31).
>     >> I am just having a normal insert statement into cf_question table.
>     >
>     > Are there any other triggers on the tables?
>
>     I'm fairly confident that the duplicates are from updates on the
>     cf_question table. Since the trigger also fires on update and then
>     inserts another record, that would explain the duplication pretty
>     well.
>
>     Nevertheless, if there are other triggers those bear investigation.
>     --
>     If you can't see the forest for the trees,
>     Cut the trees and you'll see there is no forest.
>
>


--
Adrian Klaver
adrian.klaver@aklaver.com