title: Restriction the results for relation
body: <p>I have simple tables Post and Comment and I am doing query:</p>
  
  <pre><code>$repository = $this-&gt;getDoctrine()
      -&gt;getRepository('AppBundle:Post');
  
  $query = $repository-&gt;createQueryBuilder('p')
      -&gt;where('p.made = :made')
      -&gt;setParameter('made', 1)
      -&gt;leftJoin('p.comments', 'c')
      -&gt;andWhere('c.isAdmin = :isAdmin')
      -&gt;setParameter('isAdmin', 1)
      -&gt;getQuery();
  
  $results = $query-&gt;getResult();
  
  foreach($results as $post) {
      echo $post-&gt;getId(); // this clause where (-&gt;where('p.made = :made')) working ok
      foreach($post-&gt;getComments() as $comments) {
         echo $comment-&gt;getId(); //this clause where (-&gt;andWhere('c.isAdmin = :isAdmin')) not working. This return all results
      }
  }
  </code></pre>
  
  <p>So how can I use clause where in query with relations? </p>
  
  <p>SQL:</p>
  
  <pre><code>SELECT 
    i0_.id AS id0, 
    i0_.made AS made1, 
    i0_.name AS name2, 
  FROM 
    post i0_ 
    LEFT JOIN comment i1_ ON i0_.id = i1_.comment_id 
  WHERE 
    i0_.made = ? 
    AND i1_.isAdmin = ?
  </code></pre>