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Subject: Re: choose_bitmap_and again (was Re: [PERFORM] StrangelyVariable
	Query Performance)
From: "Simon Riggs" <simon@2ndquadrant.com>
To: "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: <pgsql-hackers@postgreSQL.org>,
	"PostgreSQL Performance" <pgsql-performance@postgreSQL.org>,
	"Steve" <cheetah@tanabi.org>
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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Initially, we say this is a beta-only feature and may be withdrawn in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