title: How to correctly rollback commit with Solr's DirectUpdateHandler2?
body: <p>In Solr 5.5 (launched in embedded mode) I'm creating some bunch of documents, commit them and then I'm trying to rollback my last commit. Here is what I'm calling in my code:</p>
  
  <pre><code>UpdateHandler updateHandler = core.getUpdateHandler()
  ... // some docs
  UpdateHandler#addDoc
  UpdateHandler#commit 
  </code></pre>
  
  <p>Check the index - everything is ok, index contains all docs.</p>
  
  <p>But when I call <code>UpdateHandler#rollback</code> and check the index - nothing get changed... </p>
  
  <p>what is the problem ? should I commit after rollback ?</p>