title: Elasticsearch inner query support
body: <p>I am trying to do inner query on Elasticsearch  similar to an example on solr wiki</p>
  
  <p><a href="https://wiki.apache.org/solr/Join" rel="nofollow noreferrer">https://wiki.apache.org/solr/Join</a></p>
  
  <pre><code>SELECT xxx, yyy
  FROM collection1
  WHERE outer_id IN (SELECT inner_id FROM collection1 where zzz = "vvv")
  </code></pre>
  
  <p>Is it possible to do something similar in Elasticsearch ?</p>