How can I query for direct descendants only?

Question

Let's say I have entities a, b and c all of the same type, and the situation is like this:

entity a is parent for entity b entity b is parent for entity c

Now if I do the following query

query = ndb.Query(ancestor=a.key)
result = query.fetch()

The result will contain both b and c entities. Is there a way I can filter out c so that only entities that are direct descendants remain? Any way apart from me going through the results and removing them I mean.

Answer 1

The only way to do this is to modify your schema, adding a 'parent' KeyProperty that references an entity's direct parent, then filtering on that.

Answer 2

Actually, this is not supported at all. Nick's answer does work but only if you can specify the entity kind in your query which the OP did not specify:

"Kindless queries cannot include filters on properties. They can, however, filter by Entity Key by passing Entity.KEY_RESERVED_PROPERTY as the property name for the filter. Ascending sorts on Entity.KEY_RESERVED_PROPERTY are also supported."