如何查询过滤器自外键

Question

    query = Services.objects.filter(parent_id__isnull=True,sub_service__type=0)

当我过滤 sub_service__type=1 它 returns 正确的输出。即 type 1 对应 sub_service，但是当我将其更改为 sub_service__type=0 时，filters 不起作用。相反，它 returns 我每次输出。即 type 0,1 而不是 type 0

代码如下：

# MODELS

class Services(models.Model):
    type_ = ((1, 'INCLUSIVE'),
             (0, 'EXCLUSIVE'))
    service_id = models.AutoField(primary_key=True)
    parent_id = models.ForeignKey('self', on_delete=models.SET_NULL, null=True, blank=True, related_name='sub_service')
    type = models.SmallIntegerField(blank=True, null=True, choices=type_)


# VIEWS

@action(detail=False, methods=['get'], permission_classes=(AllowAny,))
def service_list(self, request):

    query = Services.objects.filter(parent_id__isnull=True,sub_service__type=0)
    serializer = ServiceSerializer(query , many=True).data
    return Response(serializer)


# SERIALIZER

class SubServiceSerializer(serializers.ModelSerializer):

    class Meta:
        model = Services
        fields = "__all__"


class ServiceSerializer(serializers.ModelSerializer):
    sub_service = SubServiceSerializer(many=True)

    class Meta:
        model = Services
        fields = "__all__"

Answer 1

如果您使用 sub_service__type=1 进行过滤，您会检索所有 Service 具有至少一个相关 Service 与 type=1。但是因此允许存在其他具有不同类型的相关子Service。 .sub_service 管理器还将不过滤相关对象的查询集。

您也可以使用 Prefetch object [Django-doc] 来过滤关系：

from django.db.models import <strong>Prefetch</strong>

query = Services.objects.filter(
    parent_id__isnull=True,sub_service__type=0
).prefetch_related(<strong>Prefetch(</strong>'sub_service', Service.objects.filter(type=0)<strong>)</strong>)

如何查询过滤器自外键

how to query filter self foreign key

django

django-models

django-views