AbstractA is AbstractB "base" class.........
AbstractB is ClassA "base" class............
Everything work fine in this case.
I just want to set 'polymorphic_identity' on each inheritance level
if I set by hand : update abstract_a set class_name = 'class_a' :
AbstractA.query.first() give me back a ClassA object
2010/8/15 Michael Bayer <mike...@zzzcomputing.com>
>
> On Aug 15, 2010, at 6:52 AM, jean-philippe serafin wrote:
>
> > Hi,
> >
> > I've got a class mapping with two polymorphic inheritance :
> >
> > class AbstractA(Base):
> >
> > __tablename__ = "abstract_a"
> >
> > id = Column(Integer, primary_key=True)
> > class_name = Column('class_name', String(50))
> >
> > __mapper_args__ = {
> > 'polymorphic_on': class_name,
> > }
> > #some stuff here
> >
> > class AbstractB(AbstractA):
> >
> > __tablename__ = "abstract_b"
> >
> > id = Column(Integer, ForeignKey('abstract_a.id'),
> > primary_key=True)
> > class_name = Column('class_name', String(50))
> >
> > __mapper_args__ = {
> > 'polymorphic_on': class_name,
> > 'polymorphic_identity': __tablename__,
> > }
> > #some stuff here
> >
> > class ClassA(AbstractB):
> >
> > __tablename__ = "table_a"
> > __mapper_args__ = {
> > 'polymorphic_identity': __tablename__,
> > }
> >
> > id = Column(Integer, ForeignKey('abstract_b.id'),
> > primary_key=True)
> > label = Column('label', String(50))
> >
> > def __init__(self, label):
> > self.label = label
> >
> > I persist a ClassA object :
> >
> > object = ClassA('toto')
> > db_session.add(object)
> > db_session.commit()
> >
> > When I try to reload the object like this :
> >
> > reloaded_object = AbstractB.query.first()
> >
> > I get back a ClassA object (just fine)
> >
> > but when I try to reload like this :
> >
> > reloaded_object = AbstractA.query.first()
> >
> > I get back a AbstractA object because abstract_a.class_name has not
> > been set to polymorphic_identity.
> >
> > Is this an issue or expected work?
>
> polymorphic_on only goes on the base class. SQLA should be changed to
> raise an error on the setup you have above.
>
>
> >
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