title: Is it possible to do Solr faceting combining multiple fields, like distinct on multiple columns in RMDB?
body: <p>Let's say I want to do faceting on the combination of two fields in my doc.</p>
  
  <p>For example:</p>
  
  <pre><code>Field1  Field2
  A        B
  C        D
  A        B
  A        C
  C        B
  C        D
  </code></pre>
  
  <p>Will have the facet result like</p>
  
  <pre><code>AB [2]
  CD [2]
  AC [1]
  CB [1]
  </code></pre>
  
  <p>Is this possible? I mean on the fly, which means the fields are picked randomly, and therefore cannot create a copyfield during index.</p>