Michael Bayer ha scritto:
> On Apr 3, 2007, at 11:26 AM, Glauco wrote:
>
>
>> Yes, but i lost generative methods filter_by
>>
>>
>
> First of all, filter_by() has no interaction with instances(). with
> instances(), no SQL is constructed by the Query object - it takes the
> result set of whatever exact select() statement youve constructed and
> thats it. its roughly equivalent functionality to hibernate's
> session.createSQLQuery(). its used when you know the exact SQL you
> want to issue and youd rather not have Query build the SQL for you.
>
> so as far as getting columns in conjunction with filter_by(), we are
> only talking about add_column() and add_entity().
>
> so basically youre saying that this:
>
> session.query(MyClass).filter_by(foo='bar').list()
>
> will return instances of MyClass, while this:
>
> session.query(MyClass).filter_by(foo='bar').add_column
> ('somecolumn').list()
>
> will return a result set of "somecolumn". but *not* MyClass. thats
> probably not what people expect.
>
> the only way I can see this happening would be some new method:
>
> session.query(MyClass).filter_by(foo='bar').remove_entity
> (MyClass).add_column('somecolumn').list()
>
> or perhaps:
>
> session.query(MyClass).filter_by(foo='bar').set_column
> ('somecolumn').list()
>
>
>
i think set_column is a good choice, because in big mapper ( or big
select over a lot of tables ) the sa and DB must manipulate a lot of
unused fields.
another example is a mapper i've done overa a join (i call it a mapper
ove a view) in this case i must do it for retrieve the cartesian product
of the 3 tables, but all time the result object is bigger than what i'm
searching for. For this reason i want to optimize memory occupation of
result object.
Thank you
Glauco
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Glauco Uri - Programmatore
glauco(at)allevatori.com
Sfera Carta Software® [EMAIL PROTECTED]
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