Re: - Slow Query

hum thanks a lot for the quick answer,

if is not abuse of your patience

what is the best alternative to the LEFT OUTER JOINS?

RC

On Wed, Jul 1, 2009 at 6:12 PM, Mike Ivanov <mikei(at)activestate(dot)com> wrote:

> > Merge Join (cost=111885.70..319492.88 rows=13016048 width=620)
>
> The outermost merge join has to go through 13 million rows. If you remove
> "distinct on (bien.uid)", you'll see that.
>
> > LEFT outer JOIN ville ON ville.uid = bien.ref_ville
> > LEFT outer JOIN freguesia_ville ON freguesia_ville.ref_ville =ville.uid
>
> This is not enough. You have to add this condition as well:
>
> AND bien.ref_ville = freguesia_ville.ref_ville
>
> In other words, when you link three tables by a common field, all three
> relationships should be explicitly expressed, otherwise you'll have this
> type of explosive row multiplication.
>
> Although I don't quite understand the purpose of the query, I don't think
> you need all those OUTER joins.
>
> Regards,
> Mike
>
>