Google Cloud Platform for Developers

Entity groups

All Datastore entities are part of exactly one entity group, which is a hierarchical ordering of related entities based on their ancestry paths. An entity with no ancestors is known as a root entity, and a root entity with no descendants is a member of its own entity group, where that group is composed of that single entity. When an entity lists another entity in it's ancestry path, the two entities are part of the same entity group. Because a single ancestor may have multiple descendants, entity groups may take on tree-like structures:

A Datastore entity group with a root and two descendants; note that properties may vary between ...