title: Use highlight in ElasticSearch with _source:false
body: <p>Just wanted to know.
  Is it possible to highlight text in ElasticSearch on an index with _source = false ?</p>
  
  <p>I mean i know if ES doesn't have the document he can't do the highlight but is there a way to just use ES as an highlight engine instead of a full search engine with highlights?
  (I provide the full document in the highlight query)</p>
  
  <p>Thanks</p>