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Re: EXISTS vs IN vs OUTER JOINS

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Joe Conway <mail(at)joeconway(dot)com>
Cc: 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 22:46:20
Message-ID: 6981.1040337980@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
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.

			regards, tom lane

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Subject: Re: EXISTS vs IN vs OUTER JOINS
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