title: ElasticSearch sorting doesn't work
body: <p>I am trying to do sorting by "timestamp" field (which is not a "_timestamp" default).
  "timestamp" field stores micro-unixtime in</p>
  
  <pre><code>"_source": {
     ...
     "timestamp": "1381256450000" 
     ...
  }
  </code></pre>
  
  <p>On screenshot you can see this value in 'sort' (right side). Last record should be definitely on the top of the result. But it isn't.</p>
  
  <p>Screenshot:
  <img src="https://i.stack.imgur.com/8Er4L.jpg" alt="ESquery"></p>