John A Meinel <john@arbash-meinel.com> writes:
> Unfortunately, because Hash Join doesn't report the number of rows
> (rows=0 always), it's hard to tell how good the estimator is.
This is only a cosmetic problem because you can just look at the number
of rows actually emitted by the Hash node's child; that's always exactly
the number loaded into the hashtable.
(But having said that, it is fixed in CVS tip.)
You may be confused though --- the Hash node is not the Hash Join node.
A zero report from Hash Join does actually mean that it emitted zero
rows.
regards, tom lane