From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Christoph Berg <christoph.berg@credativ.de>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1
Date: Mon, 13 May 2013 16:14:06 -0400
Message-ID: <11475.1368476046@sss.pgh.pa.us> (raw)
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References: <20130430112055.GA27525@msgid.df7cb.de>
<CA+Tgmobe3UH50Uhq=NLFj5GvgMgq2qMohguhOFBqhEgcMtKx=w@mail.gmail.com>
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Robert Haas <robertmhaas@gmail.com> writes:
> The planner is estimating this the outer side of this nested loop will
> produce 33 rows and that the inner side will produce 1. One would
> assume that the row estimate for the join product couldn't be more
> than 33 * 1 = 33 rows, but the planner is estimating 62335 rows, which
> seems like nonsense.
You know, of course, that the join size estimate isn't arrived at that
way. Still, this point does make it seem more like a planner bug and
less like bad input stats. It would be nice to see a self-contained
example ...
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, christoph.berg@credativ.de
Subject: Re: RT3.4 query needed a lot more tuning with 9.2 than it did with 8.1
In-Reply-To: <11475.1368476046@sss.pgh.pa.us>
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