joined-table inheritance and ambiguous foreign keys

[Seth P]

The code below produces the error message below. How do I tell SQLAlchemy that the inheritance join condition should be b.id == a.id rather than b.parent_a_id == a.id? (I would think the primary_key=True could be a hint...) I can't figure it out from the documentation.

class A(Base):
    __tablename__ = 'a'
    id = Column(Integer, primary_key=True)

class B(A):
    __tablename__ = 'b'
    id = Column(Integer, ForeignKey('a.id'), primary_key=True)
    parent_a_id = Column(Integer, ForeignKey('a.id'))

sqlalchemy.exc.AmbiguousForeignKeysError: Can't determine join between 'a' and 'b'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly.

Thanks,

Seth

[Michael Bayer]

its a mapper arg called inherit_condition:  __mapper_args__ = {"inherit_condition": id==A.id}

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[Seth P]

Thank you.

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