from sqlalchemy import Column, ForeignKey, Integer, create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, sessionmaker
Base = declarative_base()
class Parent(Base):
__tablename__ = 'parents'
id = Column(Integer, primary_key=True)
class Child(Base):
__tablename__ = 'children'
id = Column(Integer, primary_key=True)
parent_id = Column(Integer, ForeignKey(Parent.id))
parent = relationship(Parent, lazy='raise', passive_deletes=True)
engine = create_engine('sqlite:///:memory:', echo=True)
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()
# Add
parent = Parent()
session.add(parent)
session.flush()
child = Child(parent_id=parent.id)
session.add(child)
session.commit()
# Delete
child = session.query(Child).first()
session.delete(child)
session.commit()
Now I'm getting the following warning:
/.venv/lib/python3.8/site-packages/sqlalchemy/orm/relationships.py:2021:
SAWarning: On Child.parent, 'passive_deletes' is normally configured on one-
to-many, one-to-one, many-to-many relationships only.
If I change `parent` relationship as follows:
parent = relationship(Parent, lazy='raise', backref=backref('children',
passive_deletes=True))
then I would get the following exception:
sqlalchemy.exc.InvalidRequestError: 'Child.parent' is not available due to
lazy='raise'
How should it be made properly?
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http://www.sqlalchemy.org/
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