Django select_related doesn't optimize query - django

Question

I have a problem with select_related. I don't know what I'm doing wrong but it doesn't work..
models.py
class OrganizerUser(models.Model):
"""This user manage Agents"""
user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
def __str__(self):
return self.user.username
class Agent(models.Model):
user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
organizer = models.ForeignKey(OrganizerUser, blank=True, null=True,
on_delete=models.CASCADE)
def __str__(self):
return self.user.username
class Lead(models.Model):
first_name = models.CharField(max_length=20)
last_name = models.CharField(max_length=20)
age = models.IntegerField(default=0)
organizer = models.ForeignKey(OrganizerUser, on_delete=models.CASCADE)
agent = models.ForeignKey(Agent, null=True, blank=True, on_delete=models.SET_NULL)
category = models.ForeignKey(
Category, related_name="categories", null=True, blank=True, on_delete=models.SET_NULL
)
description = models.TextField()
date_added = models.DateTimeField(auto_now_add=True)
phone_number = models.CharField(max_length=20)
email = models.EmailField()
converted_date = models.DateTimeField(null=True, blank=True)
def __str__(self):
return f"{self.first_name} {self.last_name}"
views.py
class LeadsApiView(generics.ListCreateAPIView):
serializer_class = LeadSerializer
permission_classes = [IsAuthenticated, IsAdminOrOrganizer]
def get_queryset(self):
user = self.request.user
#if user.is_staff:
#return Lead.objects.select_related('organizer', 'agent').all()
if user.is_organizer:
return Lead.objects.select_related('organizer').filter(
organizer=user.organizeruser)
else:
return Lead.objects.select_related('agent').filter(agent=user.agent)
serializers.py
class LeadSerializer(serializers.ModelSerializer):
class Meta:
model = Lead
fields = ['id', 'first_name', 'last_name', 'age',
'organizer', 'agent', 'category', 'description', 'date_added',
'phone_number', 'email', 'converted_date'
]
for agents everything is fine. Django makes 3 queries but for other users, it makes extra queries for each existing user.

Answer 1

This solution solved the problem
How to always prefetch_related for a specific django model
class UsersManager(models.Manager):
def get_queryset(self):
return super().get_queryset().select_related('user')
class OrganizerUser(models.Model):
"""This user manage Agents"""
user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
objects = UsersManager()
def __str__(self):
return self.user.username
class Agent(models.Model):
user = models.OneToOneField(settings.AUTH_USER_MODEL, on_delete=models.CASCADE)
organizer = models.ForeignKey(OrganizerUser, blank=True, null=True,
on_delete=models.CASCADE)
objects = UsersManager()
def __str__(self):
return self.user.username