Re: Mystefied at poor performance of a standard query

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "David logan" <djlogan2(at)comcast(dot)net>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Mystefied at poor performance of a standard query
Date: 2008-10-01 13:30:12
Message-ID: 8396.1222867812@sss.pgh.pa.us
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"David logan" <djlogan2(at)comcast(dot)net> writes:
> (The question is why this simple select takes me 20 minutes to run...)

What have you got work_mem set to? The hash join is not going to be
real fast if it has to split the join into multiple batches, so you
want work_mem large enough to hold the whole inner relation. That would
be at least 20MB in this example, probably quite a bit more after
allowing for per-row overhead in the table.

regards, tom lane

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