Django - 注释多个 Sum() 对象会给出错误的结果

Question

models.py看起来像这样

class Channel(Model):
    name = CharField()

class Contract(Model):
    channel = ForeignKey(Channel, related_name='contracts')
    fee = IntegerField()

class ContractPayment(Model):
    contract = ForeignKey(Contract, related_name='payments')
    value = IntegerField()

当我查询模型时：

Channel.objects.annotate(pay=Sum('contracts__fee'))

它返回：75000。它是正确的，但是当我这样查询时：

Channel.objects.annotate(pay=Sum('contracts__fee'))
               .annotate(paid=Sum('contracts__payments__value'))

它返回：pay: 96000,paid: 33000。如您所见，薪酬已更改。这里发生了什么？我读了票#10060但没有运气。

Answer 1

使用两个查询来获得所需的结果：

Channel.objects.annotate(pay=Sum('contracts__fee'))

和

Channel.objects.annotate(paid=Sum('contracts__payments__value'))