Hi,
I'm using SqlAlchemy 0.6.3 and PostgreSQL 8.4 and I'm trying to setup
a cascading delete between several levels of tables. The problem seems
to be that I can't have a relationship with cascade="all" and a column
with ForeignKey that has nullable=False.
Here is my example:
from sqlalchemy import create_engine, Table, Column, Integer, String,
MetaData, ForeignKey
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship
engine = create_engine('postgresql://tsq:passt%qw...@localhost:5432/
ce_cascade_test', echo=True)
Session = scoped_session(sessionmaker())
Base = declarative_base()
Session.configure(bind=engine)
s = Session()
class User(Base):
__tablename__ = "users"
id = Column(Integer, primary_key=True)
name = Column(String)
device = relationship("Device", uselist=False)
@classmethod
def create(cls, user_name, device_name, manufacturer):
new_user = User()
new_user.name = user_name
new_user.device = Device.create(device_name)
return new_user
class Device(Base):
__tablename__ = "devices"
id = Column(Integer, primary_key=True)
name = Column(String)
user_id = Column(Integer,
ForeignKey('users.id'),
nullable=False)
manufacturer_id = Column(Integer,
ForeignKey('manufacturers.id'),
nullable=False)
user = relationship("User",
uselist=False,
cascade="all")
@classmethod
def create(cls, name):
new_device = Device()
new_device.name = name
return new_device
Base.metadata.create_all(engine)
user = User.create("bob", "iphone")
s.add(user)
s.commit()
s.delete(user)
s.commit()
If I run this then I get an Integrity error during the delete (because
it is updating the user_id to null before deleting it). I would like
to keep the nullable=False on the ForeignKey.
I've tried adding ondelete="CASCADE" to the ForeignKey and adding
passive_deletes=True to the relationship but it always throw the same
Integrity error.
I know I'm missing something but I can't find it in the docs, what am
I missing?
Thanks for your help,
BEN
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