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Re: RE : RE : BUG #3519: Postgres takes the wrong query plan resulting in performance issues

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Mouhamadou Dia <MDia(at)accovia(dot)com>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: RE : RE : BUG #3519: Postgres takes the wrong query plan resulting in performance issues
Date: 2007-08-06 20:57:56
Message-ID: 46B78B54.3020602@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-bugs
Hmm. I don't see anything terribly wrong in the planner's estimates. The
only estimate that's off is the # of rows in pror_org matching the qual
orgt_cd = 'CHAIN', 27 estimated vs 1 actual. You could try increasing
the statistics target for that column to get that estimate right. That
might tip the planner to choose a plan with nested loop joins instead of
hash joins.

Have you played with enable_seqscan=off or enable_hashjoin=off? That's
not a good long term solution, but it would be interesting to see what
happens.

Mouhamadou Dia wrote:
> Sorry,
> This output is coming from PG 8.1.19
> I'm attaching the one that is coming from 8.2.4
> Thanks and sorry for the confusion
> 
> 
> -----Message d'origine-----
> De : Heikki Linnakangas [mailto:hlinnaka(at)gmail(dot)com] De la part de Heikki Linnakangas
> Envoyé : 6 août 2007 15:32
> À : Mouhamadou Dia
> Cc : pgsql-bugs(at)postgresql(dot)org
> Objet : Re: RE : [BUGS] BUG #3519: Postgres takes the wrong query plan resulting in performance issues
> 
> Mouhamadou Dia wrote:
>> I'm sending in attachment the output of the explain analyze command and the create table statements of tables involved in the query.
> 
> Wait, you said that the query takes 20 seconds on 8.2, but the explain
> analyze output says that it actually took 50 seconds. Is this the output
> from 8.2.4?
> 


-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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