Michael Paquier <michael@paquier.xyz> writes:
> Okay, that's bad. Wouldn't it be sufficient to use what the caller
> passes out as lockmode instead of enforcing AEL though?
No, because at the bottom of that function we're going to do a DROP
CONSTRAINT on the old FK constraint, and that needs AEL anyway.
If we tried to take a lesser lock first we'd just be creating a
lock-upgrade deadlock risk.
regards, tom lane