Horton

Re: Slow query: bitmap scan troubles

Claudio Freire <klaussfreire@gmail.com>

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From: Claudio Freire <klaussfreire@gmail.com>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: postgresql@foo.me.uk, postgres performance list <pgsql-performance@postgresql.org>
Date: 2012-12-05T17:43:49Z
Lists: pgsql-hackers, pgsql-performance 
On Wed, Dec 5, 2012 at 2:39 PM, Jeff Janes <jeff.janes@gmail.com> wrote:
> I'm not sure that this change would fix your problem, because it might
> also change the costs of the alternative plans in a way that
> neutralizes things.  But I suspect it would fix it.  Of course, a
> correct estimate of the join size would also fix it--you have kind of
> a perfect storm here.

As far as I can see on the explain, the misestimation is 3x~4x not 200x.

Commits

  1. Tweak genericcostestimate's fudge factor for index size.

  2. Tweak index costing for problems with partial indexes.