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From: Ken Geis <kgeis@speakeasy.org>
To: Bruno Wolff III <bruno@wolff.to>
Cc: pgsql-performance@postgresql.org
Subject: Re: bad estimates
Date: Fri, 29 Aug 2003 01:17:25 -0700
Message-ID: <3F4F0C15.6040802@speakeasy.org> (raw)
In-Reply-To: <3F4EFA35.90401@speakeasy.org>
References: <3F4E99F7.7080604@speakeasy.org>
	<20030829025109.GD4373@wolff.to>
	<3F4EBF7E.8020602@speakeasy.org>
	<20030829030156.GF4373@wolff.to>
	<3F4EC1D0.5010503@speakeasy.org>
	<20030829033818.GA5577@wolff.to>
	<3F4ECC78.7090502@speakeasy.org>
	<20030829040519.GA5746@wolff.to>
	<3F4ED1DC.50808@speakeasy.org>
	<20030829042453.GA5931@wolff.to>
	<3F4EFA35.90401@speakeasy.org>

Ken Geis wrote:
> When run on 7.3.3, forcing an index scan by setting 
> enable_seqscan=false, the query took 55 minutes to run.  The index is 
> about 660M in size, and the table is 1G.  As I mentioned before, with 
> table scans enabled, it bombs, running out of temporary space.

Man, I should wait a while before I send mails, because I keep having 
more to say!

Some good news here.  Doing the same as above on 7.4beta2 took 29 
minutes.  Now, the 7.3.3 was on reiser and 7.4 on ext2, so take that as 
you will.  7.4's index selectivity estimate seems much better; 7.3.3's 
anticipated rows was ten times the actual; 7.4's is one half of the actual.


Ken





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