如何预取相关的对象以列出已经获取的对象

Question

我在主页上显示7个随机对象。为此，我根据此答案使用解决方案：

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'
)

如果我将prefetch_related=Prefetch('productphoto_set', queryset=ProductPhoto.objects.order_by('pk'))传递给random_impl方法，则每次产品一次预取1张照片。这不足为奇。我可以在获取产品后手动预取相关对象吗？

Answer 1

令我惊讶的是，有一种法律方式。记录在。您只需要添加：

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