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From: Simon Riggs <simon@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-hackers@postgreSQL.org
Cc: PostgreSQL Performance <pgsql-performance@postgreSQL.org>
Cc: Steve <cheetah@tanabi.org>
Subject: Re: choose_bitmap_and again (was Re: [PERFORM] StrangelyVariable Query Performance)
Date: Sat, 14 Apr 2007 09:24:07 +0100
Message-ID: <1176539048.3635.316.camel@silverbirch.site> (raw)
In-Reply-To: <26399.1176504501@sss.pgh.pa.us>
References: <57271CC2-BCB1-4ACA-A177-4FF64F1BC33F@brandeis.edu>
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	<26399.1176504501@sss.pgh.pa.us>

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Initially, we say this is a beta-only feature and may be withdrawn in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