title: How use filter in following case .
body: <p>How would I do the following query:</p>
  
  <p><strong>Post.objects.filter(Length('comment')>5)</strong></p>
  
  <pre><code>class Post(models.Model):   
      title = models.CharField(max_length=200)
      text = models.TextField()
  class Comment(models.Model):
      text = models.CharField(max_length=100)
      post = models.ForeignKey(Post)
  </code></pre>
  
  <p>Basically, I need to get all <code>posts</code> items having  more than 5 comment.</p>