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Re: Group-count estimation statistics

From: Manfred Koizar <mkoi-pg(at)aon(dot)at>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Group-count estimation statistics
Date: 2005-01-31 19:35:25
Message-ID: 0n1tv0p0ufe7f75hgsnj3l5l2dblarim45@email.aon.at (view raw or flat)
Thread:
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On Mon, 31 Jan 2005 11:20:31 -0500, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>Already done that way.
>            if (relvarcount > 1)
>                clamp *= 0.1;

That's not what I meant.  I tried to say that if we have a GROUP BY
several columns and one of these columns alone has more than N/10
distinct values, there's no way to get less than that many groups.

Servus
 Manfred

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