Re: Execution plan changed after upgrade from 7.3.9 to 8.2.3

> From: pgsql-performance-owner(at)postgresql(dot)org
> [mailto:pgsql-performance-owner(at)postgresql(dot)org] On Behalf Of
> vincent(dot)moreau(at)leroymerlin(dot)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