如何根据查询集中的值分配对象排名

Question

我有一个查询集 returns 一个菜单列表，我想根据累积的票数为每个菜单分配一个等级有没有办法使用 django 查询表达式来实现这个？我也愿意接受任何其他建议。

查询集如下：

qs = Menu.objects.filter(Q(created_at__date__iexact=todays_date)).order_by('-投票')

而菜单class模型如下所示：

class Menu(models.Model):
    """Represents menu class model"""
    restaurant = models.ForeignKey(Restaurant,null=True,blank=True,on_delete=models.CASCADE)
    file = models.FileField(upload_to='menus/')
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    uploaded_by = models.CharField(max_length=50, null=True, blank=True)
    votes = models.IntegerField(default=0)

序列化查询集后 returns 以下数据：

[
  {
        "id": 10,
        "file": "https://res.cloudinary.com/dw9bllelz/raw/upload/v1/media/menus/index_ah660c.jpeg",
        "restaurant": "Burger King",
        "votes": 10,
        "created_at": "2021-06-03T09:33:05.505482+03:00"
    },
    {
        "id": 9,
        "file": "https://res.cloudinary.com/dw9bllelz/raw/upload/v1/media/menus/index_ah660c.jpeg",
        "restaurant": "Texas Plates",
        "votes": 2,
        "created_at": "2021-06-03T09:33:05.505482+03:00"
    },
    {
        "id": 8,
        "file": "https://res.cloudinary.com/dw9bllelz/raw/upload/v1/media/menus/index_ah660c.jpeg",
        "restaurant": "Carlito Dishes",
        "votes": 2,
        "created_at": "2021-06-03T09:33:05.505482+03:00"
    },
      {
        "id": 7,
        "file": "https://res.cloudinary.com/dw9bllelz/raw/upload/v1/media/menus/index_ah660c.jpeg",
        "restaurant": "Kram Dishes",
        "votes": 1,
        "created_at": "2021-06-03T09:33:05.505482+03:00"
    },

]

Answer 1

您可以使用数组中对象的 index 作为其索引，也可以使用 Window functions [Django docs] and use the Rank or DenseRank (Reference [Django docs]) 函数根据需要计算排名：

from django.db.models import F, Window
from django.db.models.functions import Rank


qs = Menu.objects.filter(
    Q(created_at__date__iexact=todays_date)
).annotate(
    rank=Window(
        expression=Rank(),
        order_by=F('votes').desc(),
    )
)


for menu in qs:
    print(menu.rank, menu.votes)

如何根据查询集中的值分配对象排名

How to assign ranking on objects based on a value in a queryset

django

django-orm

django-queryset

python-3.x