Re: Postgresql 8.1.4 - performance issues for select on

On Wed, Oct 18, 2006 at 02:33:49PM -0700, Jeff Davis wrote:
> On Wed, 2006-10-18 at 23:19 +0200, Dimitri Fontaine wrote:
> > Le mercredi 18 octobre 2006 23:02, Ioana Danes a ??crit :
> > > I tried the partitioning scenario but I've got into
> > > the same problem. The max function is not using the
> > > indexes on the two partitioned tables...
> > >
> > > Any other thoughts?
> >
> > Did you make sure your test included table inheritance?
> > I'm not sure the planner benefits from constraint_exclusion without selecting
> > the empty parent table (instead of your own union based view).
> >
>
> constraint exclusion and inheritance won't help him.
>
> The problem is that he has two indexes, and he needs to find the max
> between both of them. PostgreSQL isn't smart enough to recognize that it
> can use two indexes, find the max in each one, and find the max of those
> two values.

Sorry, don't have the earlier part of this thread, but what about...

SELECT greatest(max(a), max(b)) ...

?
--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)