ok.. in my case i have something like this..
class ForumGroup(db.Model):
name = db.StringProperty()
description = db.StringProperty(multiline=True)
created_at = db.DateTimeProperty(auto_now_add=True)
class Forum(db.Model):
name = db.StringProperty()
description = db.StringProperty(multiline=True)
group = db.ReferenceProperty(ForumGroup,collection_name='forums')
created_at = db.DateTimeProperty(auto_now_add=True)
Forum has a reference property group that references to ForumGroup so
now ForumGroup object has a 'forums' property that is a Query
object..
i thought that when i got a ForumGroup doing get_by_id()
simultaneously GAE made the query to get 'forums' object and so i got
so many read quota..
then i have other DB objects referenced so i can do
group = ForumGroup().get_by_id(x)
last_post_on_forum = group.forum.threads.posts.fetch(10)
On 27 ene, 08:01, Robert Kluin <[email protected]> wrote:
> Hi,
> When you access those reference properties they are fetched by key.
> Unfortunately this will happen serially, which will significantly
> impact your performance. You're not going to avoid the read
> operations without changing your schema, but you can at least improve
> the performance by doing a batch fetch on all those referenced
> entities. One way to do this would look something like:
>
> class SomeThing(db.Model):
> ref_prop = db.ReferenceProperty()
>
> @property
> def ref_prop_key(self):
> return SomeThing.ref_prop.get_value_for_datastore(self)
>
> thing = db.get(some_thing_key)
> other, entities = db.get([thing.ref_prop_key, thing.another_ref_prop_key])
>
> This trick is to then *never* directly touch thing.ref_prop because
> it will fetch the entity again.
>
> Robert
>
>
>
>
>
>
>
> On Thu, Jan 26, 2012 at 07:30, ikalbeniz <[email protected]> wrote:
> > Hi,
>
> > I have developed a forum where i have structured the database using
> > ReferenceProperties to link forum groups, forums, threads, posts and
> > users.. so a group (db.model object) has N forums that have N threads
> > with N posts..
>
> > I have a problem with the Datastore Read Operations Quota and i think
> > than can be because when i get a Group object GAE gives me all tree
> > structure so with one get_by_id i have lots of Datastore Read
> > Operations..
>
> > Can someone confirm that this is ok? How an i avoid GAE do this so if
> > i only want to show Group properties values so i dont need to acces
> > all forums belongs to the group..
>
> > thanks.
>
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