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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