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Date: Mon, 1 Jan 2007 16:14:14 +0100 (CET)
From: =?iso-8859-1?q?Rolf=20=D8stvik?= <rolfostvik@yahoo.no>
Subject: Re: Worse perfomance on 8.2.0 than on 7.4.14
To: Dave Cramer <pg@fastcrypt.com>
Cc: pgsql-performance@postgresql.org
In-Reply-To: <5AB35188-5686-4201-A182-5A0321288084@fastcrypt.com>
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--- Dave Cramer <pg@fastcrypt.com> skrev:

> 
> On 31-Dec-06, at 6:33 AM, Rolf Østvik wrote:
> 
> >
> > Hi
> >
> > I have a simple query which uses 32ms on 7.4.14
> and 1015ms on 8.2.0.
> > I guess 7.4.14 creates a better execution plan
> than 8.2.0 for this  
> > query but
> > i don't know how to get it to select a better one.
> > Explain analyse output will be found near the end
> of the e-mail.
> >
> > (I have simplified my real query to get it as
> simple as possible.  
> > The original query
> > contain 6 tables and was acceptable on 7.4.2, but
> took far too long  
> > on 8.1.4)
> >
> > I have made a test setup to compare 7.4.14, 8.1.4
> and 8.2.0.
> > 8.1.4 and 8.2.0 uses the same execution plan and
> same time to execute.
> >
> > postgresql.conf values i changed is
> > 7.4.14
> > 	Raised shared_buffers from 32MB to 128MB
> > 	Raised temp_buffers from 8MB to 32MB
> > 8.2.0
> > 	Raised shared_buffers from 32MB to 128MB
> > 	Raised temp_buffers from 8MB to 32MB
> > 	Raised work_mem from 1MB to 8MB
> >
> set effective_cache to 3G
> shared buffers should be 1G on this computer for 8.2

Thanks for the input. Did not have a big influence on
my specific problem but comments as this is very
valuable in the total setup of my server.

Best regards
Rolf Østvik

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