title: Conditional Relationship in Symfony2
body: <p>Let's say I have a Post entity, and a Comment entity. A comment can be approved or not by an admin (which is a flag in the db). The post entity has:</p>
  
  <pre><code>/**
   * @ORM\OneToMany(targetEntity="Comment", mappedBy="post")
   */
  protected $comments;
  </code></pre>
  
  <p>And I also want a second attribute which will look like:</p>
  
  <pre><code>/**
   * @ORM\OneToMany(targetEntity="Comment", mappedBy="post")
   */
  protected $approvedComments;
  </code></pre>
  
  <p>How is it possible to load only the approved comments here?</p>