Hi all,
I try to set up a many-to-many relation with an association object.
But I want something not usual: I want the child object deleted when
not owned by any parent anymore.
This is for a messages/recipients relation: the message is useless
when everybody removed it from its mailbox!
I tried that, but it doesn't work:
class Parent(meta.DeclarativeBase):
id = Column(types.Integer, primary_key=True)
class Child(meta.DeclarativeBase):
id = Column(types.Integer, primary_key=True)
class Assoc(meta.DeclarativeBase):
p_id = Column(types.Integer,
ForeignKey(Parent.id))
c_id = Column(types.Integer,
ForeignKey(Parent.id))
parent = relation(Parent,
backref=backref('children',
cascade='all, delete-orphan'))
child = relation(Child,
backref='parents',
cascade='delete-orphan')
I expect "child = relation(Child, backref='parents', cascade='delete-
orphan')" to forward deletes to child when it is an orphan. But it
looks like it forward the delete even if it is not an orphan yet...
It that configuration:
p1 = Parent()
p2 = Parent()
c = Child()
assoc1 = Assoc(parent=p1, child=c)
assoc2 = Assoc(parent=p2, child=c)
p1.children = [ ] will lead to:
- delete assoc1 (ok)
- delete c (not ok)
- update assoc2.c_id = null (not ok)
So why is it not really a delete-orphan? :)
Thanks
GustaV
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