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Re: Optimizer refuses to hash join

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stan Bielski <bielski(at)ece(dot)cmu(dot)edu>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Optimizer refuses to hash join
Date: 2004-07-29 17:06:26
Message-ID: 15403.1091120786@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-performance
Stan Bielski <bielski(at)ece(dot)cmu(dot)edu> writes:
> I having a great deal of difficulty getting postgres to do a hash join.
> Even if I disable nestloop and mergejoin in postgres.conf, the optimizer
> still refuses to select hash join.

Are you sure the join condition is hashjoinable?  You didn't say
anything about the datatypes involved ...

If it is, the other possibility is that you need to increase sort_mem
to accommodate the hash table.

			regards, tom lane

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