title: Can you refer to and filter on a script field in a query expression, after defining it?
body: <p>I'm new to ElasticSearch and was wondering, once you define a script field with mvel syntax, can you subsequently filter on, or refer to it in the query body as if it was any other field?</p>
  
  <p>I can't find any examples of this while same time I don't see any mention of whether this is possible on the docs page</p>
  
  <p><a href="http://www.elasticsearch.org/guide/reference/modules/scripting/" rel="noreferrer">http://www.elasticsearch.org/guide/reference/modules/scripting/</a>
  <a href="http://www.elasticsearch.org/guide/reference/api/search/script-fields/" rel="noreferrer">http://www.elasticsearch.org/guide/reference/api/search/script-fields/</a></p>
  
  <p>The book ElasticSearch Server doesn't mention if this is possible or not either</p>