title: Google App Engine Datastore: How to get entity by ID/Name if parent key is unknown?
body: <p>There are two kinds of entity: User and Trip. User is parent to Trip and Trip is child to User.</p>
  
  <p>For privacy consideration I am POSTing only Trip ID/Name. Because it is looks like a Trip Key contains encoded User ID/Name.</p>
  
  <p>How to get entity by ID/Name if parent key is unknown?</p>