title: How do you implement cascading delete in Objectify?
body: <p>I have the following heriacy. </p>
  
  <p>GrandParent --> Parent --> Child</p>
  
  <p>Parent and Child use <code>@Parent Ref&lt;GrandParent&gt;</code> and <code>@Parent Ref&lt;Parent&gt;</code> to create there parent relationship.</p>
  
  <p>I am trying to come of with a good way to do a cascading delete for <code>GrandParent</code>.</p>
  
  <p>I of course I could load all the children, generate keys from them and delete by key. This seems terribly inefficient. Is there something where I could query by parent and turn the query results into a list of keys without having to do the full fetch?</p>
  
  <p>Any thoughts, or third party libraries welcome.</p>