I've encountered what I believe to be a bug in SQLAlchemy (versions 0.8.0 and 0.8.1) in a query that joins class/tables that use joined inheritance.
In the code below, I would expect the three queries to produce the same output, namely [u'CCC'], but the first one gives a different (incorrect) result, [u'BBB']. Is this a bug, or is the query malformed? In the second query, adding a seemingly gratuitous join with D fixes the problem. And as the third query shows, replacing C by an aliased version also fixes the problem. So whatever is going on seems rather subtle. Thanks, Seth from sqlalchemy import Column, Integer, String, ForeignKey, create_engine from sqlalchemy.ext.declarative.api import declarative_base from sqlalchemy.orm import relationship, sessionmaker, scoped_session from sqlalchemy.orm.util import aliased Base = declarative_base(object) metadata = Base.metadata class A(Base): __tablename__ = 'A' idx = Column(Integer, primary_key=True) name = Column(String(20), nullable=False) type_idx = Column(Integer, nullable=False) __mapper_args__ = { 'polymorphic_on':type_idx } class B(A): __tablename__ = 'B' idx = Column(Integer, ForeignKey(str(A.__table__) + ".idx"), primary_key=True) __mapper_args__ = { 'polymorphic_identity':2 } class C(A): __tablename__ = 'C' idx = Column(Integer, ForeignKey(str(A.__table__) + ".idx"), primary_key=True) b_idx = Column(Integer, ForeignKey(str(B.__table__) + ".idx"), nullable=False) b = relationship("B", foreign_keys=[b_idx]) __mapper_args__ = { 'polymorphic_identity':3 } class D(A): __tablename__ = 'D' idx = Column(Integer, ForeignKey(str(A.__table__) + ".idx"), primary_key=True) __mapper_args__ = { 'polymorphic_identity':4 } class CtoD(Base): __tablename__ = 'CtoD' idx = Column(Integer, primary_key=True) c_idx = Column(Integer, ForeignKey(str(C.__table__) + ".idx"), nullable=False) c = relationship("C", foreign_keys=[c_idx]) d_idx = Column(Integer, ForeignKey(str(D.__table__) + ".idx"), nullable=False) d = relationship("D", foreign_keys=[d_idx]) if __name__ == '__main__': engine = create_engine('sqlite:///:memory:', echo=False) metadata.create_all(bind=engine) Session = scoped_session(sessionmaker(bind=engine)) session = Session() # populate tables with a single entry in each table b = B(name='BBB') c = C(name='CCC', b=b) d = D(name='DDD') c_to_d = CtoD(c=c, d=d) session.add_all([b, c, d, c_to_d]) session.commit() sql_query = session.query(B, C.name).join(C, B.idx == C.b_idx).join(CtoD, C.idx == CtoD.c_idx).join(D, CtoD.d_idx == D.idx) print [name for (_, name) in sql_query.all()] # [u'BBB'] sql_query = session.query(B, C.name).join(C, B.idx == C.b_idx).join(CtoD, C.idx == CtoD.c_idx) print [name for (_, name) in sql_query.all()] # [u'CCC'] aliased_C = aliased(C) sql_query = session.query(B, aliased_C.name).join(aliased_C, B.idx == aliased_C.b_idx).join(CtoD, aliased_C.idx == CtoD.c_idx).join(D, CtoD.d_idx == D.idx).join(D, CtoD.d_idx == D.idx) print [name for (_, name) in sql_query.all()] # [u'CCC'] -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sqlalchemy+unsubscr...@googlegroups.com. To post to this group, send email to sqlalchemy@googlegroups.com. Visit this group at http://groups.google.com/group/sqlalchemy. For more options, visit https://groups.google.com/groups/opt_out.