And the conclusion is that we don't want to do what you are doing here, and that it would be better to store NOT NULL constraints in a way similar to CHECK constraints.
Thanks for the link to those thread.
Judging from the discussion there, it will be a long way to prevent DROP NOT NULL. So for this problem (pg_upgrade failing because of it), i propose that we only add a check in pg_upgrade, so anyone using pg_upgrade can know and fix the issue before the error?
If it's OK, i can write the patch.
> How about: ".. if some parent has the same" > > + heap_close(parent, AccessShareLock); > > Maybe, we shouldn't be dropping the lock so soon.
Yes, such things usually need to be kept until the end of the transaction, and usually you need to be careful about potential lock upgrades that could cause deadlocks. This patch looks wrong for both of those things.
Thanks. Judging from above, it's better that we continue the DROP NOT NULL problem in another patch (and another thread)
