Message-ID: <5194D54C.6030901@optionshouse.com>
Date: Thu, 16 May 2013 07:47:08 -0500
From: Shaun Thomas <sthomas@optionshouse.com>
Reply-To: <sthomas@optionshouse.com>
Organization: Peak6
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To: Thomas Kellerer <spam_eater@gmx.net>
CC: <pgsql-performance@postgresql.org>
Subject: Re: Thinking About Correlated Columns (again)
References: <5193AA62.2040700@optionshouse.com> <kn0r9o$5je$1@ger.gmane.org>
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On 05/15/2013 03:31 PM, Thomas Kellerer wrote:

> What happens if you create one index for each column? (instead of one
>  combined index)

I just created the combined index to simplify the output. With two 
indexes, it does the usual bitmap index scan. Even then the row estimate 
is off by a factor of 1000, which is the actual problem.

The other reason I tried the combined index was that there was some 
noise a while back about having the planner check for possible column 
correlations on composite indexes. Clearly that ended up not being the 
case, but it was worth examination.

-- 
Shaun Thomas
OptionsHouse | 141 W. Jackson Blvd. | Suite 500 | Chicago IL, 60604
312-676-8870
sthomas@optionshouse.com

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