title: Updating existing documents in elasticsearch
body: <p>Is it possible add more fields to existing documents in elasticsearch?</p>
  
  <p>I indexed for instance the following document:</p>
  
  <pre><code>{
      "user":"xyz",
      "message":"for increase in fields"
  }
  </code></pre>
  
  <p>Now I want to add 1 more field to it i.e date:</p>
  
  <pre><code>{
      "user":"xyz",
      "message":"for increase in fields",
      "date":"2013-06-12"
  }
  </code></pre>
  
  <p>How can this be done?</p>