On Nov 9, 2009, at 1:09 PM, David Gardner wrote:
>
> Actually I hadn't realized that the problem only occurred on
> eagerloading.
>
> Would it make sense to be able to do an alias at the table level? In
> other words:
>
> task_parent=aliased(task_table)
> mapper(Task,task_table, properties={
> 'Children' : relation(Task, backref=backref('Parent',
>
> primaryjoin=(and_(task_parent.c.asset==task_table.c.parent_asset,
>
> task_parent.c.name==task_table.c.name)),
> remote_side=[task_parent.c.asset,
> task_parent.c.name]),
> order_by=task_table.c.asset,cascade='all',
> lazy=True)
> })
that wouldn't work for a variety of reasons. aliased() doesn't work
at that level. you'd at least want to use a table alias, i.e.
task_table.alias() - but then you'd need to map the class twice, and
then you're dealing with something totally different.
there's a way to make this work which I'll eventually get to in ticket
1612.
>
>
> Michael Bayer wrote:
>> Theres a test case like this which had a behavioral change as of
>> 0.5.5, but looking at that, eager loading doesn't come into the
>> picture.
>>
>> for that particular test, we add foreign_keys=[task.c.parent_asset]
>> to
>> the many to one side, and foreign_keys=[None] to the one-to-many
>> side. You might need that here just in general.
>>
>> But for eagerloading I actually don't think we have a solution for
>> that right now. the "task_1" comes into the ON clause by way of
>> clause adaption, which has a list of columns that it wants to
>> "adapt". So "task.name" is either in or not in the list.
>>
>> I'm thinking of a completely bizarre hack which would be to add a
>> Column to the table with the same name as "name", but a different
>> key,
>> then setting up primaryjoin using that. But I don't know if that
>> would do it.
>>
>> Otherwise you might just take the easy route and say:
>>
>> t2 = aliased(Task)
>> s.query(Task).join(t2, and_(Task.parent_asset==t2.asset,
>> Task.name==t2.name)).options(contains_eager("parent" , alias=t2))
>>
>>
>>
>
>
> --
> David Gardner
> Pipeline Tools Programmer
> Jim Henson Creature Shop
> [email protected]
>
>
>
> >
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