On May 6, 2013, at 3:21 PM, V'Raj Kanwade <viraj.kanw...@gmail.com> wrote:
> Hi,
>
> I have 2 tables: Members & GroupMembers
>
> orm.mapper(Member, meta.Members)
> orm.mapper(GroupMember, meta.GroupMembers
> properties={
> 'member': orm.relation(Member,
> primaryjoin=meta.GroupMembers.c.memberID == meta.Members.c.id,
> lazy=False)
> }
> )
>
> I want to do something like
> query = session.query(GroupMember).order_by(GroupMember.member.name)
>
> I get "AttributeError: Neither 'InstrumentedAttribute' object nor
> 'Comparator' object has an attribute 'name'" error.
>
> I can do something like
> query = session.query(GroupMember).join(Member).order_by(Member.name)
> but this results in multiple joins on the same table.
query(GroupMember).join(Member).order_by(Member.name) is the right answer, and
only generates one JOIN. The second join you're seeing is due to your
lazy=False, and is a separate concern which cannot be used to impact the query
results - see
http://docs.sqlalchemy.org/en/rel_0_8/orm/loading.html#the-zen-of-eager-loading
for background on this, as well as
http://docs.sqlalchemy.org/en/rel_0_8/orm/loading.html#contains-eager which is
probably what you'll end up doing.
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