Re: increase index performance

From: Matthew Wakeling
Subject: Re: increase index performance
Date: ,
Msg-id: alpine.DEB.2.00.0905141118360.2341@aragorn.flymine.org
(view: Whole thread, Raw)
In response to: Re: increase index performance  ("Ow Mun Heng")
Responses: Re: increase index performance  ("Ow Mun Heng")
List: pgsql-performance

Tree view

increase index performance  (Thomas Finneid, )
 Re: increase index performance  (Greg Smith, )
  Re: increase index performance  (Thomas Finneid, )
  Re: increase index performance  (Matthew Wakeling, )
   Re: increase index performance  (Thomas Finneid, )
    Re: increase index performance  ("Ow Mun Heng", )
     Re: increase index performance  (Matthew Wakeling, )
      Re: increase index performance  ("Ow Mun Heng", )

On Thu, 14 May 2009, Ow Mun Heng wrote:
> Shouldn't BITMAP indexes come into play?
>
> Does having one index w/ 3 parameters being better than 3 index w/ 3
> different parameters be better for BITMAP index seeks?

I'll let someone correct me if I'm wrong, but using a single index that
exactly covers your search is always going to be better than munging
together results from several indexes, even if the planner decides to turn
it into a bitmap index scan (which will be more likely in PG8.4 with
effective_concurrency set).

Matthew

--
 I don't want the truth. I want something I can tell parliament!
                                              -- Rt. Hon. Jim Hacker MP


pgsql-performance by date:

From: Tom Lane
Date:
Subject: Re: UNION ALL and sequential scans
From: Scott Carey
Date:
Subject: Re: AMD Shanghai versus Intel Nehalem