Re: simpler query significantly slower

twanger(at)smartvia(dot)de writes:
> select
> distinct
> gruppen_produkte.produktgruppen_id
> from
> r_gruppen_produkte
> where
> r_gruppen_produkte.gruppen_id = gruppen.gruppen_id // this and the next cond are removed in 2nd query
> and
> gruppen.parent_id=1
> and
> r_gruppen_produkte.gruppen_id = r_personen_bereiche.g_id
> and
> r_personen_bereiche.p_id = 1234

This SQL seems rather seriously confused. It looks to me like you will
get back one copy of each distinct produktgruppen_id value appearing in
gruppen_produkte. Since no gruppen_produkte field is constrained by
WHERE, none will be eliminated. All that the rest of the query does is
cause a completely useless Cartesian-product join against some subset
of r_gruppen_produkte * gruppen * r_personen_bereiche.

Possibly you meant to select from r_gruppen_produkte.

BTW, PG 7.1 would have complained about the lack of FROM entries for
gruppen_produkte, gruppen, and r_personen_bereiche, which might have
clued you to your error ...

regards, tom lane