Re: mis-estimation on data-warehouse aggregate creation

From: Kris Jurka <books(at)ejurka(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: mis-estimation on data-warehouse aggregate creation
Date: 2004-11-17 08:19:39
Message-ID: Pine.BSO.4.56.0411170315050.13112@leary.csoft.net
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On Tue, 16 Nov 2004, Simon Riggs wrote:

> The join condition has so many ANDed predicates that we assume that this
> will reduce the selectivity considerably. It does not, and so you pay
> the cost dearly later on.
>

Yes, that makes a lot of sense. Without some incredibly good cross-column
statistics there is no way it could expect all of the rows to match.
Thanks for the analysis.

Kris Jurka

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