Hi again, I implemented a relationship using back_populates using the example http://docs.sqlalchemy.org/en/latest/orm/inheritance.html#relationships-with-concrete-inheritance
But I stumbled in a problem: My super class A does not have a table, it is based in a polymorphic union (thanks Michael for the great tip in my last post). X<->A A <-- L1 A<--L2 ... XMapper = mapper(X, C_table, properties={ 'resources': relationship(A,collection_class=set,*back_populates='action'* )}) AMapper = mapper(A,pjoin,with_polymorphic=('*', pjoin),polymorphic_on=pjoin.c.type) L1Mapper = mapper(L1,L1_table,inherits=AMapper, concrete=True, polymorphic_identity='l1',properties={ 'action' : relationship(X,primaryjoin=(X_table.c.id==L1_table.c.id_idx),back_populates='resources' ) #... (L2 is pretty much the same) This produces an error because my A mapper does not implement the *resources *relationship: "sqlalchemy.exc.InvalidRequestError: Mapper 'Mapper|A|pjoin' has no property 'action'" But If I remove the first *back_populates='action'*, it works. Well, for a read only collection... My question is this: is there a way to make SQLAlchemy understand that class A is abstract and therefore does not implements the relationship? Or is there another option , such as declaring action as a property? I tried that, but without much success. By the way, in my experience (what I can recall), no other ORM tool automatically allows this kind of complex bidirectional behaviour with concrete inheritance ;) that would be awesome. -- 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.