title: Dynamic order in django-mptt
body: <p>I am using a django-mptt package for my comments application and I have following model for this:</p>
  
  <pre><code>class Comment(MPTTModel):
      content = models.TextField(verbose_name='Treść')
      author = models.ForeignKey(AUTH_USER_MODEL, verbose_name='Autor', blank=False, null=True)
      is_deleted = models.BooleanField(verbose_name='Komentarz usunięty', default=False,
                                       help_text='Zaznacz, aby usunąć komentarz')
  
      ip = models.GenericIPAddressField(default=0, verbose_name='Adres IP')
  
      content_type = models.ForeignKey(ContentType, verbose_name='Typ obiektu')
      object_id = models.PositiveIntegerField(verbose_name='ID obiektu')
      content_object = GenericForeignKey('content_type', 'object_id')
      parent = TreeForeignKey('self', null=True, blank=True, related_name='children', db_index=True)
      hotness = models.FloatField(default=0)
  
      created_at = models.DateTimeField(auto_now_add=False, verbose_name='Data dodania')
  
      updated_at = models.DateTimeField(auto_now=True, verbose_name='Aktualizacja')
  
      class MPTTMeta:
          order_insertion_by = ('-hotness', '-created_at')
  
      class Meta:
          verbose_name = 'Komentarz'
          verbose_name_plural = 'Komentarze'
  
      def __unicode__(self):
          if len(self.content) &gt; 50:
              return self.content[:50] + '...'
          else:
              return self.content
  </code></pre>
  
  <p>I would like to give user possibility to sort comment tree by hotness or creation date. Is it possible to edit <code>order_insertion_by</code> field from view to generate 2 types of sorting(by date, by hotness)? Thanks for your help.</p>