如何与预取相关和预取聚合

Question

我有两个模型诊所和诊所信用：我想要一个诊所列表和可用余额的总和问题是如果我使用注释，我必须循环使用诊所信用查询集：

class Clinic(models.Model):
    """
    clinic model
    """
    user = models.OneToOneField(User, related_name="clinic", primary_key=True, 
     on_delete=models.CASCADE)

    def __str__(self):
        return self.name

    class Meta:
        db_table = 'clinic'




 class ClinicCredits(models.Model):
 """
  credit details for clinic
 """
    clinic = models.ForeignKey(Clinic, on_delete=models.CASCADE, related_name='c_credits')
    credits = models.FloatField('credits', default=0.0)
    balance = models.FloatField('balance', default=0.0, help_text="balance after deduction of credits")

    def __str__(self):
        return self.clinic.name

    class Meta:
       db_table = 'clinic_credits'

这是我获取诊所的查询：

    clinics = Clinic.objects.filter(practice_id__in=user.dietitian.practiceid).order_by(
        'user__date_joined').prefetch_related(Prefetch('c_credits',ClinicCredits.objects.filter(balance__gt=0),'credit_'))

以及我如何在这种情况下使用聚合，或者是否有其他方法可以使用可用积分来检索诊所列表。

Answer 1

您可以尝试这样使用annotate(...)：

clinics = Clinic.objects.filter(
    practice_id__in=user.dietitian.practiceid
).order_by('user__date_joined').prefetch_related(
    Prefetch(
        'c_credits',
        ClinicCredits.objects.filter(balance__gt=0),
        'credit_'
    )
).annotate(
    total_cred=Sum('c_credits__balance')
)