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To: Manfred Koizar <mkoi-pg@aon.at>
Cc: "scott.marlowe" <scott.marlowe@ihs.com>,
	pgsql-hackers@postgresql.org
Subject: Re: Correlation in cost_index() 
In-reply-to: <kjvopusi65nsige1l7le9tmf6ds8acd6ne@4ax.com> 
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Comments: In-reply-to Manfred Koizar <mkoi-pg@aon.at>
	message dated "Thu, 03 Oct 2002 19:39:44 +0200"
Date: Thu, 03 Oct 2002 14:50:00 -0400
Message-ID: <11083.1033671000@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
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Manfred Koizar <mkoi-pg@aon.at> writes:
> Never mind!  I just stumbled over those lines in selfuncs.c where
> indexCorrelation is calculated by dividing the correlation of the
> first index column by the number of index columns.

Yeah, I concluded later that that was bogus.  I've been thinking of
just using the correlation of the first index column and ignoring
the rest; that would not be great, but it's probably better than what's
there.  Have you got a better formula?

			regards, tom lane