Re: Optimizing a request

Hi,

Le Mardi 31 Août 2004 20:59, Jean-Max Reymond a écrit :
> explain SELECT art_id, art_titre, art_texte, rub_titre
> FROM article inner join rubrique on article.rub_id = rubrique.rub_id
> where rub_parent = 8;
>
> Hash Join  (cost=8.27..265637.59 rows=25 width=130)
>   Hash Cond: ("outer".rub_id = "inner".rub_id)
>   ->  Seq Scan on article  (cost=0.00..215629.00 rows=10000000 width=108)
>   ->  Hash  (cost=8.26..8.26 rows=3 width=22)
>         ->  Index Scan using rubrique_parent on rubrique
> (cost=0.00..8.26 rows=3 width=22)
>               Index Cond: (rub_parent = 8)
>

What are the values in rub_parent ... is their many disparity in the values ?
May be you have most of the value set to 8 ... and may be the optimizer think
a seq scan is better than the use of an index ...

Could you do a simple :
SELECT rub_parent, count(rub_id)
   FROM rubrique
 GROUP BY rub_parent;

Just to see the disparity of the values ...

regards,
--
Bill Footcow