I want it mapped to an object because I want to have some
properties/methods that can be executed on each row of the results that
will do some additional logic.
On Tuesday, March 25, 2014 6:21:31 PM UTC-4, Michael Bayer wrote:
>
>
> On Mar 25, 2014, at 2:43 PM, Michael Robellard
> <mi...@robellard.com<javascript:>>
> wrote:
>
> > Hello, I have what seems like a simple problem, but the only solution I
> have come up with so far isn't very good. I have a large complex query that
> is hand optimized that is built from aggregates and other data from
> different mapped tables. I can create a query for it by doing
> Session.query([column names]).from_statement(query).params({}) and that
> works just fine, but rather than each row being a KeyedTuple, I would like
> each row to be mapped to an object of a class, so that I can create some
> properties and methods on the object
> >
> > When I tried
> http://docs.sqlalchemy.org/en/rel_0_9/orm/mapper_config.html#mapping-a-class-against-arbitrary-selectsI
> get an error about not having a primary key defined
> >
> > I did get this to kind of work with Bundles, but it looks ugly and you
> have to dereference the bundle
> >
> > Here's a gist of the code:
> https://gist.github.com/subssn21/0f7300203aa39536ff5d
> >
> > What's the right way to handle this?
>
> the query you have there is entirely fixed. You can map to this if you
> wanted (using mapper() with text()) but as this is read only and has no
> malleability at all, you might as well just map a dictionary to it:
>
> class ShiftPunchData(object):
> def some_method(self):
> pass
>
> @classmethod
> def load_data(cls, session):
> for row in session.execute(“ your big query goes here”):
> s = ShiftPunchData()
> s.__dict__.update(row)
> yield s
>
> you’d get the same effect. of course theres no relationships or eager
> loading or anything like that but you’re working with an enormous fixed
> query so none of that applies anyway.
>
> now if OTOH you want to build a flexible mapping based on that general
> query idea, you’d want to express most or all of it in terms of a SQL
> expression, either a core expression or ORM. It depends on what you want
> to be able to do with it.
>
>
>
>
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