I am porting some code from SQLA .48 to .53 . I have a relation that
works in .48, but not in .53.
At the end of this post is a test program demonstrating the problem.
The program works in .48 but fails in .53 trying to understand the
child1_object relation . The error message says to add foreign_keys to
the relation, but that doesn't seem to actually help.
It does however work if I change the relation to
child1_object = relation('Child1', backref='others', primaryjoin =
child1_id == Child1.__table__.c.id)
Is making this change the recommended solution? Is the behavior I am
seeing here expected? Is the message telling me to use foreign_keys
bogus?
Here is the code:
#!/usr/bin/python -u
from sqlalchemy import Column, Integer, create_engine, String, ForeignKey
from sqlalchemy.orm import sessionmaker, relation
from sqlalchemy.ext.declarative import declarative_base
Base = declarative_base()
class Parent(Base):
__tablename__ = 'parent'
id = Column(Integer, primary_key=True)
_cls = Column('cls', String(50))
__mapper_args__ = dict(polymorphic_on = _cls )
class Child1(Parent):
__tablename__ = 'child1'
__mapper_args__ = dict(polymorphic_identity = 'child1')
id = Column(Integer, ForeignKey('parent.id'), primary_key=True)
class Child2(Parent):
__tablename__ = 'child2'
__mapper_args__ = dict(polymorphic_identity = 'child2')
id = Column(Integer, ForeignKey('parent.id'), primary_key=True)
class Other(Base):
__tablename__ = 'other'
id = Column(Integer, primary_key=True)
child1_id = Column(Integer, ForeignKey('child1.id'))
child1_object = relation('Child1', backref='others', primaryjoin =
child1_id == Child1.id)
engine = create_engine('sqlite://')
Base.metadata.create_all(engine)
session = sessionmaker(engine)()
def main():
child1 = Child1()
child2 = Child2()
other = Other()
child1.others = [other]
session.add(child1)
session.add(child2)
session.add(other)
session.flush()
assert 2 == session.query(Parent).count()
assert child1 == session.query(Other).one().child1_object
if __name__ == '__main__':
main()
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