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Re: Query times change by orders of magnitude as DB ages

From: Richard Neill <rn214(at)cam(dot)ac(dot)uk>
To:
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Query times change by orders of magnitude as DB ages
Date: 2009-11-26 16:04:32
Message-ID: 4B0EA710.4090407@cam.ac.uk (view raw or flat)
Thread:
Lists: pgsql-performance

Sergey Aleynikov wrote:
> Hello,
> 
> 2009/11/25 Richard Neill <rn214(at)cam(dot)ac(dot)uk>:
> 
> Also, if you find odd statistics of freshly analyzed table - try
> increasing statistics target, using
> ALTER TABLE .. ALTER COLUMN .. SET STATISTICS ...
> 
> If you're using defaults - it's again low for large tables. Start with
> 200, for example.

Thanks. I already had it set way up: 3000.

Is there a good description of exactly what analyse does, and how?
(in particular, what sort of statistics it gathers).

Richard

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