带有额外过滤器的 Django 查询集

Question

我的models.py如下：

class Prescription(models.Model):
    date_prescribed = models.DateTimeField()
    doctor = models.ForeignKey(Doctor)  
    pharmacy = models.ForeignKey(Pharmacy)

class Doctor(models.Model):
    name = models.CharField(max_length=150)  
    age = models.PositiveSmallIntegerField()

class Pharmacy(models.Model):
    name = models.CharField(max_length=150)
    status = models.CharField()

我现在需要找到六个月内按月分组的所有处方，以今天的月份为开始月份，可以追溯到六年前 month.I 尝试在 shell 上玩了一下，得到了此查询有效：

end_date = timezone.now()
start_date = end_date - relativedelta(months=6)    
qs = (Prescription.objects.extra(select={'month': connection.ops.date_trunc_sql('month', 'date_prescribed')})
                            .filter(date_prescribed__range=(start_date,end_date))
                            .annotate(Count('id'))
                            .order_by('month'))

但是，在视图中使用时同样不起作用：

class PrescriptionTrendListView(generics.ListAPIView):
    queryset = Prescription.objects.all()
    serializer_class = LineGraphSerializer

    def get_queryset(self):
        end_date = timezone.now()
        start_date = end_date - relativedelta(months=6)
        truncate_date = connection.ops.date_trunc_sql('month', 'date_prescribed')
        qs = super(PrescriptionTrendListView,self).get_queryset.extra(select={'month': truncate_date})
        return qs.filter(date_prescribed__range=(start_date, end_date)).annotate(pk_count=Count('pk')).order_by('month')

我收到错误消息 "function object has no attribute extra"。我做错了什么？

Answer 1

你的超级函数调用有错字（你没有调用它）

qs = super(PrescriptionTrendListView,self).get_queryset().extra(select={'month': truncate_date})

带有额外过滤器的 Django 查询集

Django queryset with extra filter

python

django

views

django-queryset