Re: Trigger with WHEN clause (WIP)

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:
> That argument is based on a completely evidence-free assumption, namely
> that this patch would make your case faster. Executing the WHEN tests
> is hardly going to be zero cost. It's not too hard to postulate cases
> where implementing a filter this way would be *slower* than doing it
> inside the trigger.

It's pretty often the case (IME) that calling a trigger is the only
point in the session where you fire plpgsql, and that's a visible
cost. Last time I had to measure it, it was 1ms per call. We were trying
to optimize queries running in 3ms to 4ms, called more than 100 times a
second (in parallel on multi core architecture, but still).

The way I understand it, having the WHEN clause in CREATE TRIGGER would
allow to filter out some interpreter initialisations.

Regards,
--
dim