Google App Engine Query (not filter) for children of an entity

Question

Are the children of an entity available in a Query?

Given:

class Factory(db.Model):
    \"\"\" Parent-kind \"\"\"
    name = db.StringProperty()

class P         


        

Answer 1

Although ancestor is described as a "filter", it actually just updates the query to add the ancestor condition. You don't send a request to the datastore until you iterate over the query, so what you have will work fine.

One minor point though: 500 entities with the same parent can hurt scalability, since writes are serialized to members of an entity group. If you just want to track the factory that made a product, use a ReferenceProperty:

class Product(db.Model):
   factory = db.ReferenceProperty(Factory, collection_name="products")

You can then get all the products by using:

myFactory.products