One small objection is that we'd lose the ability to separately display the time spent building the hash table in EXPLAIN ANALYZE output. It's probably not super important, but might be a reason to keep two plan nodes in the tree.
Would a separate hash node help for these kinds of queries in the future:
SELECT * FROM table WHERE id IN (1,2,3,4,...massive list of scalars, ...);
Chris
---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
