Re: No hash join across partitioned tables?

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Kris Jurka <books@ejurka.com>
Cc: pgsql-performance@postgresql.org
Date: 2009-04-17T15:02:34Z
Lists: pgsql-hackers, pgsql-performance
Kris Jurka <books@ejurka.com> writes:
> So the default disable_cost isn't enough to push it to use the hash join 
> plan and goes back to nestloop.  Since disable_cost hasn't been touched 
> since January 2000, perhaps it's time to bump that up to match today's 
> hardware and problem sizes?

I think disable_cost was originally set at a time when costs were
integers :-(.  Yeah, there's probably no reason not to throw another
zero or two on it.

Is there another issue here besides that one?  I think you were hoping
that the hash join would be faster than the alternatives, but the cost
estimate says it's a lot slower.  Is that actually the case?

			regards, tom lane