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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Steve <cheetah@tanabi.org>
Cc: Scott Marlowe <smarlowe@g2switchworks.com>
Cc: PostgreSQL Performance <pgsql-performance@postgresql.org>
Subject: Re: Strangely Variable Query Performance
Date: Thu, 12 Apr 2007 20:20:06 -0400
Message-ID: <10503.1176423606@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.GSO.4.64.0704122001160.17955@kittyhawk.tanabi.org>
References: <57271CC2-BCB1-4ACA-A177-4FF64F1BC33F@brandeis.edu>
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	<Pine.LNX.4.64.0704121000570.32187@glacier.frostconsultingllc.com>
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Steve <cheetah@tanabi.org> writes:
> Either way, it runs perfectly fast.  So it looks like the indexes are 
> confusing this query like you suspected.  Any advise?

Wow --- sometimes grasping at straws pays off.  I was testing here with
just a subset of the indexes to save build time, but I bet that one of
the "irrelevant" ones is affecting this somehow.  Time to re-test.

If you have some time to kill, it might be interesting to vary that
begin/rollback test script to leave one or two other indexes in place,
and see if you can identify exactly which other index(es) get it
confused.

I'm about to go out to dinner with the wife, but will have a closer
look when I get back, or tomorrow morning.  We'll figure this out.

			regards, tom lane



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