如何在 Django 中为外键做注解？

Question

我需要用注释替换 _points 属性以便我有机会按此值对 Django 管理面板中的条目进行排序。

我的模特：

class CustomUser(models.Model):
    inviter = models.ForeignKey('self', on_delete=models.SET_NULL, null=True, blank=True)

    @property
    def _points(self):
        res = CustomUser.objects.filter(inviter_id=self.id).count()
        return res

我的管理员：

class CustomUserAdmin(admin.ModelAdmin):
    list_display = ['created', 'updated']

    def get_queryset(self, request):
        qs = super(CustomUserAdmin, self).get_queryset(request)
        qs = qs.annotate(points=(HOW TO CALCULATE _points HERE?).order_by('points')
        return qs

Answer 1

inviter 关系的相反方式是 customuser，因此您可以将其实现为：

from django.db.models import Count

class CustomUserAdmin(admin.ModelAdmin):
    list_display = ['created', 'updated']

    def get_queryset(self, request):
        return super().get_queryset(request).annotate(
            <strong>points=Count('customuser')</strong>
        ).order_by('-points')

不过，将 inviter 的 related_name=… [Django-doc] 重命名为 invitees 可能更有意义：

class CustomUser(models.Model):
    inviter = models.ForeignKey(
        'self',
        <strong>related_name='invitees'</strong>,
        on_delete=models.SET_NULL,
        null=True,
        blank=True
    )

    @property
    def _points(self):
        return self<b>.invitees</b>.count()

那么我们算作：

class CustomUserAdmin(admin.ModelAdmin):
    list_display = ['created', 'updated']

    def get_queryset(self, request):
        return super().get_queryset(request).annotate(
            <strong>points=Count('invitees')</strong>
        ).order_by('-points')

如何在 Django 中为外键做注解？

How to make annotation for foreign key in Django?

django

django-models

django-admin

django-annotate