Adding a filter_by() clause by default.

[RommeDeSerieux]

In my application, a lot of models have a deleted_at field which is
either null or set to a date. And in most places where i select from
those models, i only need the instances where deleted_at is null. Of
course, i can do it manually by adding just another filter_at on every
ORM operation, but that's error-prone and breaks the DRY severely.

But i've read on the sqlalchemy website that it's quite extensible, so
how can i do it automatically for certain tables? I'm looking for
something like Django ORM's custom managers.

[Michael Bayer]

using 0.5:

from sqlalchemy.orm import Query, sessionmaker

class MyQuery(Query):
def __new__(cls, entities, **kwargs):
if hasattr(entities[0], 'deleted_at'):
return Query(entities,
**kwargs).filter_by(deleted_at=None)
else:
return object.__new__(cls)

Session = sessionmaker(query_cls=MyQuery)

[Huy Do]

This is cool stuff.

huy