Are you going to submit an updated patch? I started working on your original a couple of days ago but got distracted by some family news here. I'll send it to you so that you can start from there, to avoid duplicate work.
Thanks Alvaro. PFA, a revised patch with the "NO INHERIT" support in the complete sense. I also fixed up the ALTER TABLE ONLY ... CHECK semantics as per Noah's suggestion upthread. We now allow ONLY if the table has no children currently. The pg_dump sources have also been cleaned up now that these constraints need not be dumped separately. So this is a good change overall.
Have used connoinherit as the name in the catalog and Alvaro replaced is_only references with is_no_inherit so that stays. I leave it to the eventual committer now to pick up any more variations if desired :)
