It would be cool, though ;-)

"constraint exclusion wouldn't be all that rough, would it"

There are two interpretations of that:

* Passing a predicate down to the remote side so that the remote server can use it to exclude partitions. I believe this already works.

* Using CHECK constraints on the local side so that foreign tables can be excluded on the local side. This is a little trickier because it's hard to know that there are really no tuples on the remote side that violate the constraint. It's debatable how important that is, but it does need to be handled sanely somehow if the situation arises.