| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Joe Conway <mail(at)joeconway(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Tomasz Myrta <jasiek(at)klaster(dot)net>, PgSQL Performance ML <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: EXISTS vs IN vs OUTER JOINS |
| Date: | 2002-12-19 22:52:24 |
| Message-ID: | 200212192252.gBJMqON27748@candle.pha.pa.us |
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| Lists: | pgsql-performance |
Tom Lane wrote:
> Joe Conway <mail(at)joeconway(dot)com> writes:
> > I wonder if "[NOT] IN (subselect)" could be improved with a hash table in
> > similar fashion to the hash aggregate solution Tom recently implemented?
>
> It's being worked on ;-)
>
> http://archives.postgresql.org/pgsql-hackers/2002-11/msg01055.php
>
> Assuming I get this done, the conventional wisdom that "EXISTS
> outperforms IN" will be stood on its head --- unless we add planner code
> to try to reverse-engineer an IN from an EXISTS, which is something I'm
> not really eager to expend code and cycles on.
I am looking forward to removing _that_ FAQ item. :-)
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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