title: Does Elasticsearch reindex the documents automatically each time I update them
body: <p>I have a social model where users can like photos.</p>
  
  <p>My  photo document looks like this :</p>
  
  <pre><code>{
  "id" : ... //Indexed
  "url": ...
  "likes": .. //Not indexed
  //Other properties
  }
  </code></pre>
  
  <p>My question is, as long as a photo gets likes from other users I have to update my document. Does this update make elasticsearch automatically reindex it (knowing that the "likes" property is NOT indexed in my mapping) or it's done only if my indexed properties have changed?</p>
  
  <p>My concern is performance here.</p>