sqlalchemy updates another model before deletion
python, sqlalchemy
Solution
You should pass `cascade='delete'` to the `to_user` `relationship()`. See the docs here.
The `ondelete` argument to `ForeignKey` affects the generation of DDL statements, not how the ORM behaves.
Problem
I'm using sqlalchemy with postgresql. And I'm newbie of sqlalchemy. I made forien key for model "User" called "to_user_id" to model "Invitation" and this key is not nullable. When I try to delete instance of model "User" using ``` session.delete(user) ``` And sqlalchemy set invitation's to_user_id to NULL automatically before deletion and postgresql raise following error. ``` IntegrityError: (IntegrityError) null value in column "to_user_id" violates not-null constraint ``` How can I disable it? Here's my model's definition ``` class User(Base): ''' User model ''' __tablename__='User' id = Column(Integer,primary_key=True) class Invitation(Base): ''' Invitation model ''' __tablename__ = 'Invitation' __table_args__ = (UniqueConstraint('appointment_id', 'to_user_id'),) id = Column(Integer, primary_key=True) appointment_id = Column(Integer,ForeignKey('Appointment.id', ondelete='CASCADE'), nullable=False) appointment = relationship('Appointment', backref=backref('invitations'), ) from_user_id = Column(Integer,ForeignKey('User.id', ondelete='SET NULL'), nullable=True) from_user = relationship('User', backref=backref('sent_invitations'), primaryjoin='Invitation.from_user_id==User.id') to_user_id = Column(Integer,ForeignKey('User.id', ondelete='CASCADE'), nullable=False) to_user = relationship('User',backref=backref('received_invitations'), primaryjoin='Invitation.to_user_id==User.id', ) ```