我想使用 Django 为两个外键添加两个注释。我该怎么做呢？

Question

# models.py
from django.db import models

class Elephant(models.Model):
    location = models.ForeignKey(Location, on_delete=models.CASCADE)
    families = models.ForeignKey(Families, on_delete=models.CASCADE)

def add_families_and_locations_counts(elephants):
    return elephants.annotate(
            families_number=Count('families'),
            location_number=Count('location')
    )

# Run
output = add_families_and_locations_counts(elephants)

在上面，计数不正确。如何获得正确的计数？

Answer 1

您想要计算不同的外键模型实例。

将您的注释功能更新为以下内容：

def add_families_and_locations_counts(elephants):
    return elephants.annotate(
            families_number=Count('families', distinct=True),
            location_number=Count('location', distinct=True)
    )