How to aggregate with prefetch related and prefetch - django

Question

I Have two models clinic and ClinicCredits:
I want a list of clinics withsum of available balance
The Problem is if i use annotate i have to loop for avalibale alance with queryset of cliniccredits :
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'
here is my query to fetch clinic:
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_'))
and how can i use aggregate in this condition or is there some oter way to retreive clinic list with their available credits.

Answer 1

You can try like this using 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')
)