Re: insane index scan times

Alexander Staubo escribió:
> On 6/8/07, Martijn van Oosterhout <kleptog(at)svana(dot)org> wrote:
> >On Thu, Jun 07, 2007 at 11:20:20AM -0700, Sergei Shelukhin wrote:
> >> Version is 8.1
> >> The query I originally ran returned ~4-5 rows and had a lot of other
> >> joins and filtering conditions prior to the join with the big table.
> >> Is there any way to instruct postgres to do joins in the specific
> >> order or smth?
> >
> >Not really, Postgres can rearrange joins into the order it works out to
> >be the best.
>
> Are you sure? I was under the impression that PostgreSQL could reorder
> "where" clauses, but did not yet reorder explicit joins (as opposed
> to implicit ones through, say, "in"). But perhaps it only applied to
> some types of joins.

Postgres does flatten joins, and reorders the resulting range tables as
convenient. Only in 8.2 it learned how to to reorder outer joins, but
for inner joins this has been in place for a lot longer.

--
Alvaro Herrera http://www.advogato.org/person/alvherre
"No deja de ser humillante para una persona de ingenio saber
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