| From: | "Simon Riggs" <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | <pgsql-hackers(at)postgreSQL(dot)org>, "PostgreSQL Performance" <pgsql-performance(at)postgreSQL(dot)org>, "Steve" <cheetah(at)tanabi(dot)org> |
| Subject: | Re: choose_bitmap_and again (was Re: [PERFORM] StrangelyVariable Query Performance) |
| Date: | 2007-04-14 08:24:07 |
| Message-ID: | 1176539048.3635.316.camel@silverbirch.site |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-patches pgsql-performance |
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Initially, we say this is a beta-only feature and may be withdrawn in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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