i think i had similar configuration, and i did it like one link was
using default cascading, the other was just 'all'. but i'm not sure
if yours is same, and any way i got mine via trial and error.
do play with the cascade options. also i'm not sure if u apply some
cascade on a backref what happens to the forward side.
On Thursday 15 January 2009 18:30:29 GustaV wrote:
> 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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