如何通過外鍵和多對多關係獲取一組值？

Question

我有以下型號。

class Pizza(models.Model): 
    toppings = models.ManyToManyField(
     Topping, 
     blank=True, 
     through='PizzaTopping' 
    ) 

    locations = models.ManyToManyField(
     Location, 
     blank=True, 
     through='PizzaLocations' 
    ) 

class PizzaTopping(models.Model): 
    pizza = models.ForeignKey(
     Pizza, 
     on_delete=models.CASCADE 
    ) 

    topping = models.ForeignKey(
     Topping, 
     on_delete=models.CASCADE 
    ) 

class PizzaLocations(models.Model): 
    pizza = models.ForeignKey(
     Pizza, 
     on_delete=models.CASCADE 
    ) 

    location = models.ForeignKey(
     Location, 
     on_delete=models.CASCADE 
    ) 

class Topping(models.Model): 
    topping = models.CharField(
     max_length=255, 
     null=True, 
     blank=True, 
     db_index=True) 

class Location(models.Model): 
    location = models.CharField(
     max_length=255, 
     null=True, 
     blank=True, 
     db_index=True) 

我想做到這一點查詢：

Get the most popular toppings where location = some location 

我明白我需要做的是這樣的：

• 過濾器的位置
• 獲取所使用的配料的比薩餅所有比薩餅
• 按最常見的配料排序

但是我越來越困惑。

請你幫忙解釋一下如何構建這樣一個複雜的查詢？

謝謝。

Answer 1

這是我的解決方案：

Topping.objects.filter(pizza__locations__location='Location Name').annotate(count=Count("id")).order_by('-count')