Обсуждение: Firing triggers based on certain Insert conditions

"Harpreet Dhaliwal" <harpreet.dhaliwal01@gmail.com> writes:
> I want this trigger to fire only when after Insert this field 'source'
> has value = 'from', otherwise trigger should not be fired at all.
> Just wondering if its really possible?

No, and it seems pretty silly as a feature request.  Why don't you just
put the test in the trigger, and have it do nothing when you don't want
it to do anything?

            regards, tom lane

On 1/29/07, Harpreet Dhaliwal <harpreet.dhaliwal01@gmail.com> wrote:
>
> Hi
> I have a table in which i have a field named 'source'
> A trigger is written on this table.
> I want this trigger to fire only when after Insert this field 'source'
> has value = 'from', otherwise trigger should not be fired at all.
> Just wondering if its really possible?

AFAIK you can't prevent the trigger from firing, but you can make the
trigger behave differently based on what's in the fields of the new
row:

CREATE FUNCTION source_insert() RETURNS trigger AS $$
 BEGIN
  IF NEW.source = 'from' THEN

   /* do stuff */

  END IF;

  RETURN NULL;
 END;
$$ LANGUAGE plpgsql VOLATILE;

CREATE TRIGGER post_insert AFTER INSERT ON [your table name] FOR EACH
ROW EXECUTE PROCEDURE source_insert();

Regards,
BJ