title: GAE Objectfy - Why should I add @Index on Field to use that in filter condition
body: <p>I am completely to new to <code>Objectify</code>. I am using <code>Objectify</code> for GAE application , I have one interesting question in <code>Objectify</code> <code>filter</code> condition </p>
  
  <p>I am to executing a <code>load</code> method to do some filter like</p>
  
  <pre><code>objectify.load().type(User.class).filter("email", userEmail).first().now();
  </code></pre>
  
  <p>My Question is, above  statement doesn't work until I mark <code>email</code> field in <strong>User</strong> Entity class as <code>@Index</code> ? Why is this required ? . If we don't put @Index on field, we get <code>null</code> result. </p>
  
  <p>Could some one clarify my doubt, I am little concern about marking my fields as @Index as it might <strong>cost</strong> <strong>space</strong> and it(@Index) is one of the candidate to grow data in GAE Datastore.</p>
  
  <p>Thanks to SO post <a href="https://stackoverflow.com/questions/12871579/objectify-4-filter-not-working">Objectify 4 Filter not working</a> . It helped me to solve my problem.</p>