Deleting users/groups orphans Principal

[auspex]

When a User (or presumably Group, but I didn't test that yet) is deleted, we're using:

def doDeleteUser(self, login):
    session = Session()
    user = session.query(self.user_class).filter_by(login=login).first()
    if user is None:
        return False
    session.delete(user)
    notify(PrincipalDeleted(user))
    return True

Unfortunately this leaves the user on the Principal table, and it's no longer possible to re-add the user. Surely when deleting either groups or users, we should be deleting the principal object (and I don't understand the SQLAlchemy ORM well enough yet to know whether we should do that directly or via a backref).

[malthe]

There should be a cascade-rule that deletes the principal, since it's joined to that table by inheritance. Or I could be wrong.

[auspex]

There's no cascade defined on my PostGreSQL tables - so it would have to be internal to SQLAlchemy somehow - but annoyingly I find that on my one test system it's working, and deleting the principal. On my other system, it isn't. I can't see a difference in the table structures, but that same system was giving me ugly results a week ago because they'd let it run out of space by not actually removing all the PostGreSQL backups they were making, so let's just hope it's a bad system setup.
[That's a whole other issue - PlonePAS actually swallows the "Out of space" error, silently.]

[auspex]

After making sure that both sites are running exactly the same code for pas.plugins.sqlalchemy and my own product, removing both products from both sites, deleting all the tables and sequences, and then reinstalling them, I get exactly the same problem. One site cascades the deletes, the other doesn't.

[malthe]

And SQLAlchemy-versions, they match? And the SQL-driver?

It really should just work.