Re: MERGE: performance advices

On Tue, Sep 2, 2008 at 10:58 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> "Richard Broersma" <richard(dot)broersma(at)gmail(dot)com> writes:
>> There is one possible alteration that may or many not improve
>> performance. This would be to replace the EXISTS with a LEFT JOIN
>> WHERE IS NOT NULL;
>
> That changes the behavior, doesn't it? Or is event_log_no a unique
> key for Myevents? I think what you want is to make the EXISTS an IN
> instead.

Thanks for pointing that out Tom. I hadn't consider how the EXISTS
clause would return potentially fewer rows if event_log_no wasn't
unique.

--
Regards,
Richard Broersma Jr.

Visit the Los Angeles PostgreSQL Users Group (LAPUG)
http://pugs.postgresql.org/lapug