From: "Dave Dutcher" <dave@tridecap.com>
To: <vincent.moreau@leroymerlin.fr>
Cc: <pgsql-performance@postgresql.org>
Subject: Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3
Date: Tue, 13 Mar 2007 08:24:37 -0500
Message-ID: <010401c76572$f33d33a0$2e00a8c0@tridecap.com>
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> From: pgsql-performance-owner@postgresql.org 
> [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of 
> vincent.moreau@leroymerlin.fr
> Subject: Re: [PERFORM] Execution plan changed after upgrade 
> from 7.3.9 to 8.2.3
> 
> The following did not change anything in the execution plan
> 
> ALTER TABLE lm05_t_tarif_panneau ALTER COLUMN lrg_min SET 
> STATISTICS 1000
> ALTER TABLE lm05_t_tarif_panneau ALTER COLUMN lrg_max SET 
> STATISTICS 1000
> ANALYZE lm05_t_tarif_panneau
> 
> I was able to improve response time by creating indexes, but I would 
> like to avoid changing the database structure because it is not 
> maintained by ourseleves, but by the  third party vendor.


I would actually try increasing the statistics on table
lm05_t_couleur_panneau columns ht_min, ht_max, cod_aspect, and
cod_gamme_panneau.  Because I think the planner is thrown off because the
sequential scan on lm05_t_couleur_panneau returns 280 rows when it expects
1.  Maybe to start you could just SET default_statistics_target=1000,
analyze everything, and see if that makes any difference.

Dave