Unable to delete persistent objects from Google App Engine datastore

Question

I have 2 classes AAA and BBB, where BBB contains a field of AAA type.

When I call makePersistent() on 10 AAA and 10 BBB objects, the datastore ends up with 20 AAA objects and 10 BBB objects. I understand this is normal since GAE's datastore is non-relational.

However, when I try to deletePersistentAll using the following,

pm.newQuery(BBB.class).deletePersistentAll(); pm.newQuery(AAA.class).deletePersistentAll();

All BBB objects get removed as expected, but all 20 AAA objects remain. Is there something I'm missing?