From: Tom Lane <tgl@sss.pgh.pa.us>
To: Manfred Koizar <mkoi-pg@aon.at>
Cc: scott.marlowe <scott.marlowe@ihs.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Correlation in cost_index()
Date: Thu, 03 Oct 2002 14:50:00 -0400
Message-ID: <11083.1033671000@sss.pgh.pa.us> (raw)
In-Reply-To: <kjvopusi65nsige1l7le9tmf6ds8acd6ne@4ax.com>
References: <5oropusfmcur82u3l5odpnhkbg8ha0aj5t@4ax.com>
<Pine.LNX.4.33.0210031059070.5705-100000@css120.ihs.com>
<kjvopusi65nsige1l7le9tmf6ds8acd6ne@4ax.com>
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
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, mkoi-pg@aon.at, scott.marlowe@ihs.com
Subject: Re: Correlation in cost_index()
In-Reply-To: <11083.1033671000@sss.pgh.pa.us>
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