我有一个模型，我试图通过最高评级平均顺序，但它似乎没有做正确的排序。
在我的www.example.com中views.py我有：

restaurants = Restaurant.objects.all().order_by('-rating__rating_average')

我的模型定义将字段定义为：

rating_average = models.FloatField()

然而，这个查询似乎返回了一个随机排序。我忽略了什么吗？这个查询是如何用FloatField完成的？
下面是我的models.py文件和相关模型：

class Rating(models.Model):
    restaurant = models.OneToOneField('restaurant.Restaurant', primary_key=True)
    one_star_total= models.IntegerField()
    two_star_total= models.IntegerField()
    three_star_total= models.IntegerField()
    four_star_total= models.IntegerField()
    five_star_total= models.IntegerField()
    number_of_ratings = models.IntegerField()
    total_rating_value = models.IntegerField()
    rating_average = models.FloatField()
    def __str__(self):              # __unicode__ on Python 2
        return self.restaurant.restaurant_name

class Restaurant(models.Model):
    user = models.OneToOneField(User)
    restaurant_name = models.CharField(max_length=100)
    address = models.CharField(max_length=100)
    address2= models.CharField(max_length=100, default= "null", blank=True,null=True)
    city = models.CharField(max_length=100)
    state = models.CharField(max_length=100)
    zipcode = models.IntegerField()
    phone = models.CharField(max_length=15)
    website_link= models.CharField(max_length=200, blank=True, null=True)
    category= models.CharField(max_length=100)
    pub_date = models.DateTimeField(default=timezone.now,blank=True)
    def __str__(self):              # __unicode__ on Python 2
        return self.restaurant_name