Re: Help with Trigger

On 12/28/2016 07:06 PM, Clifford Snow wrote:
> I'm trying to write a trigger (my first) to update another table if the
> user_id is new. But I'm getting a index exception that the user_id

What is the actual error message?

> already exists. I'm picking up data from another feed which gives
> provides me with changes to the main database.
>
> what I have is
>
> CREATE OR REPLACE FUNCTION add_new_user()
> RETURNS TRIGGER AS
> $BODY$
> DECLARE
> commits RECORD;
> BEGIN
> SELECT INTO commits * FROM changes WHERE user_id = NEW.user_id;

In the above you are checking whether the changes table has the user_id
and if does not then creating a new user in the user table below. Not
sure how they are related, but from the description of the error it
would seem they are not that tightly coupled. In other words just
because the user_id does not exist in changes does not ensure it also
absent from the table user. Off the top of head I would say the below
might be a better query:

SELECT INTO commits * FROM user WHERE user_id = NEW.user_id;

Though it would help the debugging process if you showed the complete
schema for both the changes and user tables.

> IF NOT FOUND
> THEN
> INSERT INTO user (user_name, user_id, change_id,
> created_date)
> VALUES(NEW.user_name, NEW.user_id,
> NEW.change_id, NEW.created_date);
> END IF;
> RETURN NEW;
> END;
> $BODY$
> LANGUAGE plpgsql;
>
> CREATE TRIGGER add_new_user_trigger
> BEFORE INSERT ON changes
> FOR EACH ROW
> EXECUTE PROCEDURE add_new_user();
>
> I hoping for some recommendations on how to fix or at where I'm going wrong.
>
> Thanks,
> Clifford
>
>
> --
> @osm_seattle
> osm_seattle.snowandsnow.us <http://osm_seattle.snowandsnow.us>
> OpenStreetMap: Maps with a human touch

--
Adrian Klaver
adrian(dot)klaver(at)aklaver(dot)com