title: Why properties referenced in an equality (EQUAL) or membership (IN) filter cannot be projected?
body: <p><a href="https://developers.google.com/appengine/docs/java/datastore/projectionqueries" rel="nofollow">https://developers.google.com/appengine/docs/java/datastore/projectionqueries</a></p>
  
  <p>Why a projected query such as this : <strong>SELECT A FROM kind WHERE A = 1</strong> not supported  ?</p>