title: Lithium mongodb distinct command with conditions
body: <p>In lithium models, I can use the <code>command()</code> to select distinct of specific field (See <a href="https://stackoverflow.com/questions/5750561/distinct-selects-in-lithium">distinct selects in lithium</a>):</p>
  
  <pre><code>$blogs = $self-&gt;connection-&gt;command(array('distinct'=&gt;'blogs', 'key'=&gt;'url'));
  </code></pre>
  
  <p>which is translated to mongodb command as:</p>
  
  <pre><code>db.blogs.distinct('url');
  </code></pre>
  
  <p>Now I want to add a condition on type='rumours' in my distinct query:</p>
  
  <pre><code>db.blogs.distinct('url', {type: 'rumours'});
  </code></pre>
  
  <p>How do I add this <code>{type: 'rumours'}</code> condition in <code>command()</code>?</p>