Hello.
I was unable to reproduce the problem on your test example. I THINK it does
exactly what my problematic code does. It seems that either the problem is more
elaborate (but I don't see it) or I have a bug somewhere in my code. However my
simple workaround works, so I consider the problem solved, at least for now. I
will try to dig deeper when I have more time.
Ladislav Lenart
On 9.11.2012 23:22, Michael Bayer wrote:
> there's no mapping or code example provided here, which makes a condition
> like this extremely difficult to diagnose, however I've prepared a test
> script that takes its best guess as to configuration, that is, a
> client_products collection with a "client" backref, and a cascade of "all,
> delete-orphan" on the one-to-many which maximizes the conditions under which
> a ClientProduct might be deleted. The test case below does not exhibit this
> behavior; please alter it such that it reproduces the condition you are
> seeing so that we can diagnose this fully and ensure you aren't coming across
> any new SQLAlchemy bugs:
>
>
> from sqlalchemy import *
> from sqlalchemy.orm import *
> from sqlalchemy.ext.declarative import declarative_base
>
> Base = declarative_base()
>
> class Client(Base):
> __tablename__ = "a"
>
> id = Column(Integer, primary_key=True)
> data = Column(String)
> client_products = relationship("ClientProduct",
> backref='client',
> cascade="all, delete-orphan")
>
>
> class ClientProduct(Base):
> __tablename__ = "b"
>
> id = Column(Integer, primary_key=True)
> data = Column(String)
> a_id = Column(Integer, ForeignKey('a.id'))
>
> e = create_engine("sqlite://", echo=True)
>
> Base.metadata.create_all(e)
>
> s = Session(e)
>
>
> s.add_all([
> Client(data='c1', client_products=[
> ClientProduct(data='cp1'),
> ClientProduct(data='cp2'),
> ClientProduct(data='cp3'),
> ]),
> Client(data='c2', client_products=[
> ClientProduct(data='cp4'),
> ClientProduct(data='cp5'),
> ClientProduct(data='cp6'),
> ]),
> ])
> s.commit()
>
>
> c1 = s.query(Client).filter_by(data='c1').one()
> c2 = s.query(Client).filter_by(data='c2').one()
>
> cp1, cp2 = c1.client_products[0:2]
>
> cp1.client = c2
> cp2.client = c2
> s.delete(c1)
> s.commit()
>
> assert s.query(Client.data).all() == [('c2',)]
> assert s.query(ClientProduct.data).all() == [('cp1', ), ('cp2', ), ('cp4', ),
> ('cp5', ), ('cp6', )]
>
>
>
>
> On Nov 8, 2012, at 11:30 AM, Ladislav Lenart wrote:
>
>> Hello.
>>
>> I have a client which has a collection of ClientProduct-s (ClientProduct has
>> a
>> FK to Client). The following code:
>>
>> # Move some client products from a duplicate to the original.
>> # Remove duplicate clients afterwards (in cascade).
>> #
>> # Note that client_map is a dict from a duplicate to its original.
>> for each_duplicate, each_client in client_map.iteritems():
>> for each_cp in each_duplicate.client_products:
>> if some_condition(each_cp):
>> each_cp.client = each_client
>> session.delete(each_duplicate)
>> session.flush()
>>
>> deletes a client product that was moved from each_duplicate to each_client in
>> the inner loop. Why? What can I do to prevent it?
>>
>>
>> Thank you in advance,
>>
>> Ladislav Lenart
>>
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