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Re: why is bitmap index chosen for this query?

From: "Steinar H(dot) Gunderson" <sgunderson(at)bigfoot(dot)com>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: why is bitmap index chosen for this query?
Date: 2006-05-18 16:46:40
Message-ID: 20060518164640.GA7291@uio.no (view raw or flat)
Thread:
Lists: pgsql-performance
On Thu, May 18, 2006 at 09:41:23AM -0700, Stephen Byers wrote:
> Does the table perchance fit completely into memory, without
> effective_cache_size indicating that?
> 
>   Don't know the exact way to answer your question, but my initial instinct is "no way."

What about the working set? Have you tried running the queries multiple times
in a row to see if the results change? It might be that your initial bitmap
scan puts all the relevant bits into cache, which will skew the results.

/* Steinar */
-- 
Homepage: http://www.sesse.net/

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