title: solr result grouping based on a certain query
body: <p>I'm trying to do some sort of "different" grouping/faceting with solr.
  The case is, we are allowing the users to search by say fields X, Y and Z</p>
  
  <p>The grouped counts are displaying have the following requirements:
  X( documents matching Y AND Z )
  Y( documents matching X AND Z )
  Z( documents matching X AND Y )</p>
  
  <p>I really don't want to run multiple queries to do this, is there a better way to do it?</p>