如何使用django ORM计算累计总和

Question

我正在尝试根据日期group_by()数据，每天我都想计算当天的计数以及迄今为止的总计数。

我得到的样本输出：

[
{
"dates": "2022-11-07",
"count": 1
},
{
"dates": "2022-11-08",
"count": 3
},
{
"dates": "2022-11-09",
"count": 33
}
]

我试图实现的样本输出：

[
{
"dates": "2022-11-07",
"count": 1,
"cumulative_count": 1
},
{
"dates": "2022-11-08",
"count": 3,
"cumulative_count": 4
},
{
"dates": "2022-11-09",
"count": 33,
"cumulative_count": 37
}
]

这是我的问题：

self.serializer_class.Meta.model.objects.all().annotate(dates=TruncDate("date__date")).values("dates").order_by("dates").annotate(count=Count("channel", distinct=True)).values("count", "dates")

如何扩展此查询以获得累计总和？

Answer 1

我试着像这个一样解决你的问题

型号.py

class Demo(models.Model):
count =models.IntegerField()
dates = models.DateField()

serializers.py

class DemoSerializer(serializers.ModelSerializer):

class Meta:
model = Demo
fields = "__all__"

视图.py

class DemoAPI(APIView):
def get(self, request, pk=None, format=None):
data = Demo.objects.all()
cumulative_count= 0
# Normal Django ORM Queruset
print('--------- Default Queryset Response ---------')
for i in data:
del i.__dict__['_state']
print(i.__dict__)
# Adding cumulative_count key in ORM Queryset   
for i in data:
cumulative_count += i.__dict__['count']
i.__dict__['cumulative_count'] = cumulative_count
# Updated Django ORM Queruset with cumulative_count 
print('--------- Updated Queryset Response ---------')
for i in data:
# del i.__dict__['_state']
print(i.__dict__)

从Queryset中删除_state键之前的输出

#--------- Default Queryset Response --------- 
{'_state': <django.db.models.base.ModelState object at 0x000001A07002A680>, 'id': 1, 'count': 1, 'dates': datetime.date(2022, 11, 7)}
{'_state': <django.db.models.base.ModelState object at 0x000001A07002A5C0>, 'id': 2, 'count': 3, 'dates': datetime.date(2022, 11, 8)}
{'_state': <django.db.models.base.ModelState object at 0x000001A07002A7A0>, 'id': 3, 'count': 33, 'dates': datetime.date(2022, 11, 9)}
#--------- Updated Queryset Response --------- 
{'_state': <django.db.models.base.ModelState object at 0x000002DAB66E0AC0>, 'id': 1, 'count': 1, 'dates': datetime.date(2022, 11, 7), 'cumulative_count': 1}
{'_state': <django.db.models.base.ModelState object at 0x000002DAB66E0C10>, 'id': 2, 'count': 3, 'dates': datetime.date(2022, 11, 8), 'cumulative_count': 4}
{'_state': <django.db.models.base.ModelState object at 0x000002DAB66E0D60>, 'id': 3, 'count': 33, 'dates': datetime.date(2022, 11, 9), 'cumulative_count': 37}

从Queryset中删除_state键后输出在Queryset中添加cumulative_count键

#--------- Default Queryset Response ---------
{'id': 1, 'count': 1, 'dates': datetime.date(2022, 11, 7)}
{'id': 2, 'count': 3, 'dates': datetime.date(2022, 11, 8)}
{'id': 3, 'count': 33, 'dates': datetime.date(2022, 11, 9)}
#--------- Updated Queryset Response ---------
{'id': 1, 'count': 1, 'dates': datetime.date(2022, 11, 7), 'cumulative_count': 1}
{'id': 2, 'count': 3, 'dates': datetime.date(2022, 11, 8), 'cumulative_count': 4}
{'id': 3, 'count': 33, 'dates': datetime.date(2022, 11, 9), 'cumulative_count': 37}