it doesn't know which class on the left side you'd like to join
from. so its looking for:
sess.query(A, B, C).join((B, A.bs), (C, B.cs))
alternatively, instead of "A.bs" etc. you can spell out the join
condition such as A.b_id==B.id in each tuple.
On Nov 8, 2008, at 3:03 PM, Greg wrote:
>
>
> This following request works fine and produce the result I was
> expecting session.query(UserRss, Rss, Item).join([Rss, Item]). But
> count doesn't work. Is it a bug, or did I miss something ?
>
>>>> str(session.query(UserRss, Rss, Item).join([Rss, Item]).count())
>
> Traceback (most recent call last):
> File "<console>", line 1, in <module>
> File "/opt/local/lib/python2.5/site-packages/SQLAlchemy-0.5.0rc3-
> py2.5.egg/sqlalchemy/orm/query.py", line 1251, in count
> return self._col_aggregate(sql.literal_column('1'),
> sql.func.count,
> nested_cols=list(self._only_mapper_zero().primary_key))
> File "/opt/local/lib/python2.5/site-packages/SQLAlchemy-0.5.0rc3-
> py2.5.egg/sqlalchemy/orm/query.py", line 241, in _only_mapper_zero
> raise sa_exc.InvalidRequestError("This operation requires a Query
> against a single mapper.")
> InvalidRequestError: This operation requires a Query against a single
> mapper.
>
> Thanks.
> Greg
>
>
> >
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