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Message-ID: <5193e08b.8271440a.1813.1075@mx.google.com>
Date: Wed, 15 May 2013 13:23:25 -0600
From: eggyknap <eggyknap@gmail.com>
To: Nikolas Everett <nik9000@gmail.com>
Cc: Heikki Linnakangas <hlinnakangas@vmware.com>, sthomas@optionshouse.com,
	"pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
Subject: Re: Thinking About Correlated Columns (again)
References: <5193AA62.2040700@optionshouse.com> <5193AF36.3040409@vmware.com>
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On Wed, May 15, 2013 at 01:30:57PM -0400, Nikolas Everett wrote:
> The option that always made the most sense to me was having folks ask
> postgres to collect the statistic by running some command that marks two
> columns as correlated.  This could at least be a starting point.

One suggestion made in the past was to calculate these stats (provided someone
comes up with something worthwhile to calculate, that is) for all columns
involved in a multicolumn index. That probably doesn't cover all the places
we'd like the planner to know stuff like this, but it's a reasonable start.

--
Joshua Tolley / eggyknap
End Point Corporation
http://www.endpoint.com

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