On Jan 29, 2009, at 11:32 AM, Werner F. Bruhin wrote:
>
> Werner F. Bruhin wrote:
>> I have some items which are related but I need to change it so they
>> related to another item.
>>
>> Before getting myself in a mess (as I need to do this for a bunch of
>> tables) I wanted to check if the following approach is fine.
>>
>> I am using SA 0.5, ORM and declarative and the model is:
>>
>> class Cbbottle(Base):
>> __table__ = sa.Table(u'cbbottle', metadata,
>> sa.Column(u'cbbottleid', sa.Integer(),
>> sa.Sequence('gen_cbbottle_cbbottleid'), primary_key=True,
>> nullable=False),
>> etc
>> )
>>
>> purchase = sao.relation('Purchase', cascade="all, delete,
>> delete-orphan", backref='cbbottle')
>>
>> aItem = session.query(db.Cbbottle).get(keyno)
>> bItem = session.query(db.Cbbottle).get(anotherkeyno)
>>
>> for purchase in aItem.purchase:
>> purchase.cbbottle = bItem
>>
>> session.commit()
>>
>> At this point I expect that aItem has no more "purchase" relations
>> and
>> they are all related to bItem.
>>
>>
> I had a go at it and get this error on a few tables:
> c:\python25\lib\site-packages\sqlalchemy-0.5.2-py2.5.egg\sqlalchemy
> \orm\properties.py:711:
> SAWarning: On Bottag.bothist, delete-orphan cascade is not supported
> on
> a many-to-many or many-to-one relationship when single_parent is not
> set. Set single_parent=True on the relation().
> self._determine_direction()
>
> Changing the relations then makes it run without error but there is
> one
> record being missed.
>
> I changed it slightly:
> aItem = session.query(db.Cbbottle).get(keyno)
> bItem = session.query(db.Cbbottle).get(anotherkeyno)
>
> for purchase in aItem.purchase:
> purchase.cbbottle = bItem
> purchase.fk_cbbottleid = bItem.cbbottleid
>
> session.commit()
>
> But for some reason one record is still not reassigned. So, what I do
> is obviously not quit right.
>
there's no need to reassign the FK column yourself and the original
pattern you're using is correct. that only one item in the list is
the exception suggests something else is changing its state again
further down the road.
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