ReferenceProperty - id access without fetching the entity - Google App Engine

Message from discussion ReferenceProperty - id access without fetching the entity

Rafe

More options Oct 2 2008, 6:02 pm

From: Rafe <slobberch...@gmail.com>

Date: Thu, 2 Oct 2008 15:02:01 -0700 (PDT)

Local: Thurs, Oct 2 2008 6:02 pm

Subject: Re: ReferenceProperty - id access without fetching the entity

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Mazia is correct, there is no guarantee that this will work. In
fact, it is very likely it will not work in the future. We may in the
future implement lazy loading so that you can access the key directly
without loading the entity (a.C.key()) however, for now, this is
guaranteed to work:

A.C.get_value_for_datastore(a).key()

On Sep 29, 6:23 pm, Andy Freeman <ana...@earthlink.net> wrote:

> Is there an approved way to copy a ReferenceProperty from one entity
> to another without fetching the referred to entity from the datastore?

> In other words,

> class C(db.Model):
> ...

> class A(db.Model):
> C = db.ReferenceProperty(reference_class=C)

> class B(db.Model):
> C = db.ReferenceProperty(reference_class=C)

> a = {some query}
> b = B()
> # I would like to do the next assignment without retrieving the
> relevant entity
> # from the data store.
> b.C = a.C

> Yes, I know that a._C.id() can be used to read the id, but that
> doesn't seem to be part of the documented interface.

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