如何預取相關對象以獲取已獲取列表的相關對象？

Question

我在主頁上顯示7個隨機對象。對於我使用基於this answer溶液：

class ProductManager(models.Manager): 
    def random(self, n_products, filter={}, select_related=None): 
     n_products_total = self.filter(**filter).count() 
     if n_products_total == 0: 
      return [] 
     r = [self.random_impl(n_products_total, filter, select_related) for i in range(n_products)] 
     return [p for p in r if p is not None] 

    def random_impl(self, n_products, filter, select_related=None): 
     random_index = randint(0, n_products - 1) 
     try: 
      return self.filter(**filter) \ 
       .select_related(select_related)[random_index] 
     except IndexError: 
      return None 

random_products = Product.objects.random(7, filter={'enabled': True}, select_related='category') 

如果我通過prefetch_related=Prefetch('productphoto_set', queryset=ProductPhoto.objects.order_by('pk'))到random_impl方法，預取在時間爲每個產品1張相片。這並不奇怪。產品已被提取後，可以手動預取相關對象嗎？

Answer 1

令我驚訝的是，有一個legal way。記錄，那是。您只需添加：

prefetch_related_objects(random_products, Prefetch('productphoto_set', queryset=ProductPhoto.objects.order_by('pk')))