title: Does supplying an ancestor improve filter queries performance in objectify / google cloud datastore?
body: <p>I was wondering which of these two is superior in terms of performance (and perhaps cost?):</p>
  
  <p>1) <code>ofy().load().type(A.class).ancestor(parentKey).filter("foo", bar).list()</code></p>
  
  <p>2) <code>ofy().load().type(A.class)                    .filter("foo", bar).list()</code></p>
  
  <p>Logically, I would assume (1) will perform better as it restricts the domain on which to perform the filtering (though obviously there's an index). However, I was wondering if I may be missing some consideration/factor.</p>
  
  <p>Thank you.</p>