Subject: Re: Fwd: 8.2 Query 10 times slower than 8.1 (view-heavy)
From: Mark Lewis <mark.lewis@mir3.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Evan Carroll <lists@evancarroll.com>, pgsql-performance@postgresql.org
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Organization: MIR3, Inc.
Date: Fri, 31 Aug 2007 17:09:17 -0700
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On Fri, 2007-08-31 at 19:39 -0400, Tom Lane wrote:
> I wrote:
> > Mark Lewis <mark.lewis@mir3.com> writes:
> >> We've been holding back from upgrading to 8.2 because this one is a
> >> show-stopper for us.
> 
> > Well, you could always make your own version with this patch reverted:
> > http://archives.postgresql.org/pgsql-committers/2006-11/msg00066.php
> > I might end up doing that in the 8.2 branch if a better solution
> > seems too large to back-patch.
> 
> I thought of a suitably small hack that should cover at least the main
> problem without going so far as to revert that patch entirely.  What we
> can do is have the IS NULL estimator recognize when the clause is being
> applied at an outer join, and not believe the table statistics in that
> case.  I've applied the attached patch for this --- are you interested
> in trying it out on your queries before 8.2.5 comes out?

Wish I could, but I'm afraid that I'm not going to be in a position to
try out the patch on the application that exhibits the problem for at
least the next few weeks.

-- Mark