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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Christophe Pettus <xof@thebuild.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: 7k records into Sort node, 4.5m out?
Date: Wed, 15 Aug 2012 16:51:12 -0400
Message-ID: <16268.1345063872@sss.pgh.pa.us> (raw)
In-Reply-To: <623F2FF3-B79D-419A-929A-41C707DD5EA3@thebuild.com>
References: <D2CA9292-023A-4DF4-82B8-6E99CE82CCB1@thebuild.com>
	<dda48e8e4cd63cc6f98f9eca78016c05.squirrel@sq.gransy.com>
	<32B51AEA-E940-40CF-BA54-C7D4E3E1F0D7@thebuild.com>
	<10304.1344910305@sss.pgh.pa.us>
	<623F2FF3-B79D-419A-929A-41C707DD5EA3@thebuild.com>

Christophe Pettus <xof@thebuild.com> writes:
> On Aug 13, 2012, at 7:11 PM, Tom Lane wrote:
>> The whole thing looks a bit weird to me --- why did it not use a
>> nestloop join with inner indexscan on charlie?  With 7000 rows on the
>> other side, the estimated cost for that shouldn't have been more than
>> about 30000 ...

> Here's the same query with set enable_megejoin = off.  All of the other query tuning parameters are default.

> 	http://explain.depesz.com/s/dqO

Maybe you had better show us the actual query, and the table/index
definitions.  Because it's sure making odd choices here.  This seems
like the wrong join order altogether ...

			regards, tom lane




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