python - 从 SerializerMethodField() 更改为 annotate()

Question

我是 django 和 django-rest-framework 的新手，我遇到了一个需要优化 API 端点的项目。发现 SerializerMethodField() 导致对 SQL 的重复查询，我认为这是 N+1 问题。我目前正在阅读并尝试探索 annotate()，但发现逻辑计算很复杂，我被困在如何将其转换为 annotate() 上。有没有人知道如何正确实施这一点？请看下面的代码。希望任何人都可以指导我，因为我已经被困了好几天了。非常感谢。

序列化程序.py：

class BootcampClassStatisticsSerializer(ModelBaseSerializer):
    attendance_rating = serializers.SerializerMethodField()

    def get_attendance_rating(self, instance):
        attendance_rating = None
        attendance_count = 0
        present_count = 0

        bootcampers = instance.bootcamper_set.all()
        date = self.context.get('date')

        for bootcamper in bootcampers:
            attendances = bootcamper.dailyattendance_set.all()
            if date:
                attendances = attendances.filter(date=date)

            present_attendances = attendances.filter(status=constants.PRESENT)
            if instance.class_type == constants.DAY:
                attendance_count += len(attendances) * 2
                for item in present_attendances:
                    if item.duration == 'wd':
                        present_count += 2
                    if item.duration == 'hd':
                        present_count += 1

            if instance.class_type == constants.NIGHT:
                attendance_count += len(attendances)
                present_count += len(present_attendances)

        if attendance_count:
            attendance_rating = round(present_count / attendance_count * 100, 2)

        return attendance_rating

    class Meta:
        model = BootcampClass
        fields = (
            'id',
            'batch_number',
            'start_date',
            'end_date',
            'class_type',
            'attendance_rating'

视图.py：

class BootcampClassStatisticsList(APIView):
    queryset = BootcampClass.objects.all()
    serializer = BootcampClassStatisticsSerializer()
    return Response(serializer, status=status.HTTP_200_OK)

标签： pythondjangodjango-rest-frameworkdjango-viewsdjango-serializer