title: diversify my solr results
body: <p>I would like diversify the results that solr gives back.
  Let's assume that this is my schema.</p>
  
  <pre><code>&lt;field name="id" type="string" indexed="true" stored="true" required="true"/&gt;
  &lt;field name="description" type="text" indexed="true" stored="true" multiValued="false" /&gt;
  &lt;field name="domain" type="text" indexed="true" stored="true" multiValued="false" /&gt;
  </code></pre>
  
  <p>For the domain field, there are currently 3 types (google, yahoo, bing) that are stored in there. </p>
  
  <p>Whenever I do a query, the top results from Solr are mostly from Yahoo domain. If I want to mix up the top results from all these 3 domains, how should I do it?</p>