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Re: Bad Plan for Questionnaire-Type Query

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From:	Tom Lane
Subject:	Re: Bad Plan for Questionnaire-Type Query
Date:	May 7, 2009 , 20:31:51
Msg-id:	25886.1241728303@sss.pgh.pa.us (view: Whole thread, Raw)
In response to:	Re: Bad Plan for Questionnaire-Type Query (David Blewett)
Responses:	Re: Bad Plan for Questionnaire-Type Query (David Blewett)
List:	pgsql-performance

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Bad Plan for Questionnaire-Type Query (David Blewett, 07 May 2009, 17:01:26 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 07 May 2009, 17:28:19 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 07 May 2009, 20:31:51 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 07 May 2009, 22:41:21 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 07 May 2009, 22:44:18 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 07 May 2009, 22:56:39 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 09 May 2009, 00:08:39 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 09 May 2009, 02:06:20 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 09 May 2009, 15:44:52 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 09 May 2009, 15:52:51 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 10 May 2009, 20:45:12 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 22 May 2009, 20:14:51 )
Re: Bad Plan for Questionnaire-Type Query (Tom Lane, 24 May 2009, 18:42:07 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 25 May 2009, 15:22:47 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 05 June 2009, 22:00:14 )
Re: Bad Plan for Questionnaire-Type Query (Josh Berkus, 05 June 2009, 23:32:57 )
Re: Bad Plan for Questionnaire-Type Query (David Blewett, 06 June 2009, 00:29:51 )
Re: Bad Plan for Questionnaire-Type Query (Robert Haas, 06 June 2009, 02:02:29 )

David Blewett <> writes:
> On Thu, May 7, 2009 at 12:53 PM, David Blewett <> wrote:
>> 1. http://dpaste.com/hold/41842/
>> 2. http://explain.depesz.com/s/Wg
>> 3. http://explain.depesz.com/s/1s
>> 4. http://dpaste.com/hold/41846/

> Forgot to mention that I'm using Postgres 8.3.6 on linux 2.6.24.

Well, the reason it likes the nestloop plan is the estimate of just one
row out of the lower joins --- that case is pretty much always going to
favor a nestloop over other kinds of joins.  If it were estimating even
as few as ten rows out, it'd likely switch to a different plan.  So the
question to ask is why the rowcount estimates are so abysmally bad.
You mentioned having tried to increase the stats targets, but without
seeing the actual stats data it's hard to speculate about this.

            regards, tom lane

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From: Robert Haas
Date: 07 May 2009, 20:25:26
Subject: Re: Transparent table partitioning in future version of PG?

From: david@lang.hm
Date: 07 May 2009, 20:52:27
Subject: Re: Transparent table partitioning in future version of PG?