Fix crash in postgres_fdw for provably-empty remote UPDATE/DELETE.
In 86dc90056, I'd written find_modifytable_subplan with the assumption
that if the immediate child of a ModifyTable is a Result, it must be
a projecting Result with a subplan. However, if the UPDATE or DELETE
has a provably-consta
Fix crash in postgres_fdw for provably-empty remote UPDATE/DELETE.
In 86dc90056, I'd written find_modifytable_subplan with the assumption
that if the immediate child of a ModifyTable is a Result, it must be
a projecting Result with a subplan. However, if the UPDATE or DELETE
has a provably-consta
