Problem with PolyModel queries

[eyalhei]

Hi,

Using google-cloud-ndb==0.2.0

I have the following classes:

class Base(PolyModel):
    status = StringProperty()
    ...

class Child(Base):
   filter_prop = StringProperty()
   projected_prop = StringProperty()

The following query throws an exception (a work around I tried for the second issue):

list(Base.query().fetch(projection=["class"]))

The Exception:

File "<env>/site-packages/google/cloud/ndb/model.py", line 4721, in _lookup_model
    ).format(kind)
google.cloud.ndb.model.KindError: No model class found for the kind 'd'. Did you forget to import it?

Would love to hear of any solution I could use for the meantime (other than removing projection...)
Thanks!

[chrisrossi]

Regarding 1)

This is indeed a bug, which I will go ahead and fix. However, even "fixed", you may find the behavior counter-intuitive. The PolyModel.class is a repeated property, and the way that Datastore handles projections of repeated properties is kind of weird.

To illustrate, here is what happens with GAE NDB using Python 2.7 (the legacy code):

from google.appengine.ext import ndb
from google.appengine.ext.ndb import polymodel

class Animal(polymodel.PolyModel):
    foo = ndb.IntegerProperty()

class Cat(Animal):
    pass

animal = Animal(foo=1)
animal.put()
cat = Cat(foo=2)
cat.put()

query = Animal.query(projection=["class"])
print query.fetch()

Gives the result:

[Animal(key=Key('Animal', 5697517501022208), class_=[u'Animal'], _projection=('class',)), 
Animal(key=Key('Animal', 5765961831415808), class_=[u'Animal'], _projection=('class',)), 
Animal(key=Key('Animal', 5697517501022208), class_=[u'Cat'], _projection=('class',))]

My fix will restore the legacy behavior. It seems unlikely you will find that useful, though.

[chrisrossi]

Regarding 2)

I suspect this is a different issue. If you don't mind, let's track it separately.

I have done some testing and haven't found anything unexpected. If there is still something you'd like to look at there, please open a separate issue and include some more detail on how to reproduce it.

Thanks!