Oh, it was so easy!
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,properties={
'action' : relationship(X) # no back_populates, it will never happens anyway
})
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'* )
Now I understand... no need for back-ref
Em sábado, 13 de julho de 2013 10h13min50s UTC-3, Alexandre Torres escreveu:
>
> 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.
>
>
>
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