On Sunday 22 June 2008 18:51:44 Michael Bayer wrote:
> On Jun 22, 2008, at 8:27 AM, [EMAIL PROTECTED] wrote:
> > hi
> > i want to fetch/eagerload just one column off a related object.
> > e.g. if
> > A.b pointing to B and B having x,y,z, i want to get all As and
> > the A.b.x, and nothing else from B.
> > it even doesnot actualy matter if it will be really A.b.x or just
> > some A.new_bx made-up column/attribute.
> >
> > can?
>
> you can:
>
> query(A, B.x).join(A.bs).all()
how do i alias those as they are all similar (e.g. B.x and C.x etc)
i do (pseudocode):
r = query(A)...
extra_name = ... #the above 'x' present in all B,C,D,...
for selector,selklas in dict(b=B,c=C,d=D).items():
r = r.add_column( getattr( selklas, extra_attrname) )
r = r.outerjoin( selector)
the error is:
Ambiguous join for entity 'B.x'; specify id=<someid> to
query.join()/query.add_column(), or use the aliased() function to use
explicit class aliases.
>
> or much less desireable:
>
> query(A).options(eagerload(A.bs), defer(B.a), defer(B.b),
> defer(B.c), ...)
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