Hi Amit.
I gone through the mail thread discussion regarding this issue and reviewed you patch.
-- Patch get applied cleanly on Master branch
-- Make and Make Install fine
-- make check also running cleanly
In the patch code changes looks good to me.
This patch having two part:
1) Allowed TableOid system column in the CHECK constraint
2) Throw an error if other then TableOid system column in CHECK constraint.
I noticed that you added test coverage for 1) but the test coverage for 2) is missing..
I added the test coverage for 2) in the attached patch.
Marking this as Ready for committer.
Regards,
Rushabh