"Thomas F. O'Connell" <tfo@xxxxxxxxxxxx> writes: > As for how this plays out in the real world, a pg_dumpall will start > and run for a few hours. Sometime during that, this function might > get called. When it does, an ACCESS EXCLUSIVE lock is held against > the table identified as t13, here directly referenced only as a > FOREIGN KEY. It's the addition of a foreign key constraint that's biting you. That requires installing triggers on the pre-existing table (t13, also t14 in your example), and that requires an exclusive lock. Since we don't currently allow any ON SELECT triggers, it's possible that adding a trigger could be downgraded to just ExclusiveLock (which wouldn't conflict with pg_dump's AccessShareLock), but I can't say that I'm enthusiastic about that idea. regards, tom lane
