Hi, I'm trying to set up a model where child objects are allowed to
not have parents. At present, I can't get SA to leave the children
intact, despite having ondelete="SET NULL" and no "delete-orphan"s.
This is with SA 0.4.3.
To demonstrate my confusion, can someone explain why this code deletes
all my hats:
import sys, time
from datetime import datetime
from sqlalchemy import Table, Column, ForeignKey, MetaData,
create_engine
from sqlalchemy.orm import relation, sessionmaker, mapper, backref
from sqlalchemy import String, Unicode, Integer, DateTime
metadata=MetaData()
engine = create_engine("sqlite:///:memory:")
users_table = Table('tg_user', metadata,
Column('user_id', Integer, primary_key=True),
)
hat_table = Table('hat', metadata,
Column('id', Integer, primary_key=True),
Column('user_id', Integer, ForeignKey('tg_user.user_id',
ondelete='SET NULL')),
)
metadata.create_all(engine)
class User(object):
pass
class Hat(object):
pass
mapper(User, users_table)
mapper(Hat, hat_table,
properties = {
'user': relation(User, backref=backref("hats",
cascade="all")),
}
)
Session = sessionmaker(bind=engine, autoflush=False,
transactional=True)
session = Session()
me = User()
me.hats.extend([Hat(), Hat(), Hat()])
session.save(me)
session.flush()
print session.query(Hat).count(), "hats"
session.delete(me)
session.flush()
print session.query(Hat).count(), "hats"
Thank you!
James
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