函数 sum(boolean) 不存在

Question

从 sqlite 切换到 postgres，我在 django 中遇到此错误

函数 sum(boolean) 不存在 第 1 行：..."."longitude", "pins_pin"."category_id", COALESCE(SUM("pins_...

提示：没有函数匹配给定的名称和参数类型。您可能需要添加显式类型转换。

视图集

class PinViewSet(viewsets.ModelViewSet):
    queryset = pin.objects.annotate(
        numOfUpvotes=Coalesce(Sum('upvoters__upvote'), Value(0))
    )
    permission_classes = [
        permissions.AllowAny
        # permissions.IsAuthenticated,
    ]
    serializer_class = PinSerializer
    filter_backends = [DjangoFilterBackend]
    filterset_fields = '__all__'

序列化器

class PinSerializer(serializers.ModelSerializer):
    username = serializers.CharField(
        source="owner.username", read_only=True)
    numOfUpvotes = serializers.IntegerField(read_only=True)
    upvoters = upVoteStorySerializer(many=True, read_only=True)
    commentstory = 
    class Meta:
        model = pin
        fields = '__all__'

class upVoteStorySerializer(DynamicFieldsMixin, serializers.ModelSerializer):
    class Meta:
        model = upVoteStory
        fields = '__all__'

型号

class pin(models.Model):
    owner = models.ForeignKey(settings.AUTH_USER_MODEL,
                              null=True, on_delete=models.CASCADE)
    title = models.CharField(max_length=50)
    description = models.TextField()
    latitude = models.CharField(max_length=50)
    longitude = models.CharField(max_length=50)
    category = models.ForeignKey(
        "categoryType", on_delete=models.CASCADE, null=True, related_name='selected_category')
    # 1 is community, 2: historical, 3: personal
    #upVotes = models.PositiveSmallIntegerField(default=0)

    def __str__(self):
        """String for representing the Model object."""
        return self.title

class upVoteStory(models.Model):
    pinId = models.ForeignKey(
        "pin", on_delete=models.CASCADE, null=True, related_name='upvoters')
    upVoter = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE, null=True)
    upvote = models.BooleanField(default=False)

numOfUpvotes 从 upvotestory 为每个 pin 计算 upvotes = true。将引脚添加到数据库时最初设置为 0。使用 sqlite 时，它​​可以工作，但是当我尝试迁移到 postgres 时，我会收到此错误。我尝试清除数据库和迁移并再次重做整个过程，python manage.py makemigrations 和 python manage.py migrate 但仍然会得到相同的错误

Answer 1

您可以使用Sum, Case, When 执行此操作，以计算每次upvoters__upvote 是True

pin.objects.annotate(
    numOfUpvotes=Sum(Case(
        When(upvoters__upvote=True, then=1),
        default=Value(0),
        output_field=IntegerField()
    ))
)