I can't really make this an FK. I can (and probably will) put this into a trigger. Although it seems like an extra layer of wrapping just to call a function. I'm curious if there's any conceptual reason why constraints couldn't (as an option) be restored after all the data is loaded, and whether there would be any negative consequences of that? I could see if your data still didn't pass the CHECKs, it's already loaded. But the constraint could then be marked not valid?
Not sure why just know that if I stay within the guidelines it works, if I do not its does not work:)
That's fair enough, leaving aside the curiosity part. Usually though the things you can't do just aren't allowed. It's easier to overlook something that you shouldn't (but can) do!
I find in life most things that are prohibited are actually doable - you're just punished if you get caught doing them. In all seriousness though I agree it would be nice if that's how this worked; but decades of historical precedent makes actual preventive enforcement difficult if not impossible.
Since "test your backups" covers this potential problem, and so many possible others, any non-trivial effort to solve the actual problem is hard to justify spending time on.
I do get the "make \d show relevant information" argument and that is one that seems easier to solve, since adding explicit dependencies during trigger creation would be a purely new feature.
