Greg Stark <gsstark(at)mit(dot)edu> writes:
> I suspect this is obvious but since you asked, there isn't any way to keep
> around the hash table and just reuse it repeatedly instead of having to rescan
> the data over and over is there?
We already do that when possible --- which it's not in the particular
case at hand, because there's an outer-query parameter used in the
hashed subplan.
It occurs to me that the planner ought to favor putting parameterized
subplans on the outside of a hash join instead of the inside, so as to
make reuse more likely. Not sure how to factor that into the cost
model though.
regards, tom lane