fix(views): optimize database queries to solve N+1 problems 🔨🐛

billing/views.py

@@ -13,6 +13,7 @@ from rest_framework.response import Response
 from api.mixins import StaffEditorPermissionMixin
 from api.tasks import add_new_devices_to_omada
 from apibase.env import BASE_DIR, env
+from django.db.models import Prefetch
 import logging
 
 from .models import Device, Payment, Topup, WalletTransaction
@@ -60,10 +61,18 @@ class ListCreatePaymentView(StaffEditorPermissionMixin, generics.ListCreateAPIVi
     filterset_class = PaymentFilter
 
     def get_queryset(self):
-        queryset = super().get_queryset()
-        if self.request.user.is_superuser:
-            return queryset
-        return queryset.filter(user=self.request.user)
+        unpaid_qs = Payment.objects.filter(paid=False).order_by("-created_at")
+        device_qs = Device.objects.prefetch_related(
+            Prefetch("payments", queryset=unpaid_qs, to_attr="unpaid_payments")
+        )
+        queryset = Payment.objects.select_related("user").prefetch_related(
+            Prefetch("devices", queryset=device_qs)
+        )
+
+        if not self.request.user.is_superuser:
+            queryset = queryset.filter(user=self.request.user)
+
+        return queryset
 
     def create(self, request):
         data = request.data
@@ -163,7 +172,7 @@ class UpdatePaymentAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
 
 class VerifyPaymentView(StaffEditorPermissionMixin, generics.UpdateAPIView):
     serializer_class = PaymentSerializer
-    queryset = Payment.objects.all()
+    queryset = Payment.objects.select_related("user").all()
     lookup_field = "pk"
 
     def update(self, request, *args, **kwargs):
@@ -322,7 +331,7 @@ class VerifyPaymentView(StaffEditorPermissionMixin, generics.UpdateAPIView):
 
 
 class CancelPaymentView(StaffEditorPermissionMixin, generics.UpdateAPIView):
-    queryset = Payment.objects.all()
+    queryset = Payment.objects.select_related("user").all()
     serializer_class = PaymentSerializer
     lookup_field = "pk"
 
@@ -352,7 +361,7 @@ class CancelPaymentView(StaffEditorPermissionMixin, generics.UpdateAPIView):
 
 
 class ListCreateTopupView(StaffEditorPermissionMixin, generics.ListCreateAPIView):
-    queryset = Topup.objects.all()
+    queryset = Topup.objects.all().prefetch_related("user")
     serializer_class = TopupSerializer
     filter_backends = [DjangoFilterBackend]
     filterset_fields = "__all__"