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Re: Fwd: 8.2 Query 10 times slower than 8.1 (view-heavy)

From: Mark Lewis <mark(dot)lewis(at)mir3(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Evan Carroll <lists(at)evancarroll(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Fwd: 8.2 Query 10 times slower than 8.1 (view-heavy)
Date: 2007-09-01 00:09:17
Message-ID: 1188605357.5367.14.camel@archimedes (view raw or flat)
Thread:
Lists: pgsql-performance
On Fri, 2007-08-31 at 19:39 -0400, Tom Lane wrote:
> I wrote:
> > Mark Lewis <mark(dot)lewis(at)mir3(dot)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

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