Re: How to read query plan

From: John Arbash Meinel <john(at)arbash-meinel(dot)com>
To: Miroslav Šulc <miroslav(dot)sulc(at)startnet(dot)cz>
Cc: PGSQL mailing list <pgsql-performance(at)postgresql(dot)org>
Subject: Re: How to read query plan
Date: 2005-03-13 17:30:25
Message-ID: 423478B1.7080106@arbash-meinel.com
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Miroslav Šulc wrote:

> Hi John,
>
> thank you for your response.
>
How about a quick side track.
Have you played around with your shared_buffers, maintenance_work_mem,
and work_mem settings?
What version of postgres are you using? The above names changed in 8.0,
and 8.0 also has some perfomance improvements over the 7.4 series.

What is your hardware? Are you testing this while there is load on the
system, or under no load.
Are you re-running the query multiple times, and reporting the later
speeds, or just the first time? (If nothing is loaded into memory, the
first run is easily 10x slower than later ones.)

Just some background info. If you have set these to reasonable values,
we probably don't need to spend much time here, but it's just one of
those things to check.

John
=:->

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