Re: choose_bitmap_and again (was Re: [PERFORM] StrangelyVariable Query Performance)

From: Simon Riggs
Subject: Re: choose_bitmap_and again (was Re: [PERFORM] StrangelyVariable Query Performance)
Date: ,
Msg-id: 1176539048.3635.316.camel@silverbirch.site
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In response to: choose_bitmap_and again (was Re: [PERFORM] Strangely Variable Query Performance)  (Tom Lane)
List: pgsql-hackers


On Fri, 2007-04-13 at 18:48 -0400, Tom Lane wrote:
> Has anyone got any thoughts about the best way to do this?

I don't think we know enough to pick one variant that works in all
cases. This requires more detailed analysis of various cases.

Lets put in a parameter to allow the options to be varied. The purpose
would be to look for some more information that allows us to see what
the pre-conditions would be for each heuristic.

Initially, we say this is a beta-only feature and may be withdrawn in
the production version.

Why did it not pick my index? is a tiring game, but one that must be
played. I hope that the ORDER LIMIT optimization should reduce the
number of indexes chosen to maintain sort order in the output.

--  Simon Riggs              EnterpriseDB   http://www.enterprisedb.com





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