SQLAlchemy: cascade delete

Question

I must be missing something trivial with SQLAlchemy\'s cascade options because I cannot get a simple cascade delete to operate correctly -- if a parent element is a deleted,

Answer 1

@Steven's asnwer is good when you are deleting through session.delete() which never happens in my case. I noticed that most of the time I delete through session.query().filter().delete() (which doesn't put elements in the memory and deletes directly from db). Using this method sqlalchemy's cascade='all, delete' doesn't work. There is a solution though: ON DELETE CASCADE through db (note: not all databases support it).

class Child(Base):
    __tablename__ = "children"

    id = Column(Integer, primary_key=True)
    parent_id = Column(Integer, ForeignKey("parents.id", ondelete='CASCADE'))

class Parent(Base):
    __tablename__ = "parents"

    id = Column(Integer, primary_key=True)
    child = relationship(Child, backref="parent", passive_deletes=True)