title: Apache Solr - search multiple different cores simultaneously (cores with different document structure)
body: <p>I have an Apache Solr installation which runs 2 cores:</p>
  
  <ul>
  <li>the Machines core</li>
  <li>the Notifications core</li>
  </ul>
  
  <p>Each core indexes a database table, so the content of the cores is completely different - by structure and actual content
  Now i would like to run a search query on both of the cores and in the end to get a single result set from the 2 cores combines. For a trivial example if I would search for "2010" I would like my results to be relevant machine documents and notification documents, each from its own core, but combined as a result set, ordered by relevance.
  Expected result set example:</p>
  
  <ul>
  <li>Machine #1</li>
  <li>Machine #2</li>
  <li>Notification #1</li>
  <li>Machine #3</li>
  <li>Notification #2</li>
  <li>Notification #3</li>
  <li>Machine #4</li>
  </ul>
  
  <p>I will be interacting with Solr through SolrJ [Java connector].</p>
  
  <p>Does anybody have any idea? Is what I am trying to do even possible ?</p>
  
  <p>Thanks!</p>