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

devices/serializers.py

@@ -36,9 +36,9 @@ class DeviceSerializer(serializers.ModelSerializer):
 
     def get_pending_payment_id(self, obj):
         unpaid_payment = (
-            Payment.objects.filter(devices=obj, paid=False)
-            .order_by("-created_at")
-            .first()
+            obj.unpaid_payments[0]
+            if hasattr(obj, "unpaid_payments") and obj.unpaid_payments
+            else None
         )
         return unpaid_payment.id if unpaid_payment else None
 
@@ -63,9 +63,9 @@ class AdminDeviceSerializer(serializers.ModelSerializer):
 
     def get_pending_payment_id(self, obj):
         unpaid_payment = (
-            Payment.objects.filter(devices=obj, paid=False)
-            .order_by("-created_at")
-            .first()
+            obj.unpaid_payments[0]
+            if hasattr(obj, "unpaid_payments") and obj.unpaid_payments
+            else None
         )
         return unpaid_payment.id if unpaid_payment else None
 

devices/views.py

@@ -3,7 +3,9 @@ from xmlrpc.client import Boolean
 from rest_framework import generics, status
 from rest_framework.response import Response
 from django_filters.rest_framework import DjangoFilterBackend
+from billing.models import Payment
 from .models import Device
+from django.db.models import Prefetch
 from .serializers import (
     CreateDeviceSerializer,
     DeviceSerializer,
@@ -28,6 +30,13 @@ class DeviceListCreateAPIView(
     filterset_fields = "__all__"
     filterset_class = DeviceFilter
 
+    def get_queryset(self):
+        unpaid_qs = Payment.objects.filter(paid=False).order_by("-created_at")
+        base_qs = Device.objects.select_related("user").prefetch_related(
+            Prefetch("payments", queryset=unpaid_qs, to_attr="unpaid_payments")
+        )
+        return base_qs.all()
+
     def list(self, request, *args, **kwargs):
         queryset = self.filter_queryset(self.get_queryset())
         all_devices = request.query_params.get("all_devices", "false").lower() in [
@@ -90,7 +99,7 @@ class DeviceDetailAPIView(StaffEditorPermissionMixin, generics.RetrieveAPIView):
 
 
 class DeviceUpdateAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
-    queryset = Device.objects.all()
+    queryset = Device.objects.select_related("user").all()
     serializer_class = CreateDeviceSerializer
     lookup_field = "pk"
 
@@ -116,7 +125,7 @@ class DeviceUpdateAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
 
 
 class DeviceBlockAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
-    queryset = Device.objects.all()
+    queryset = Device.objects.select_related("user").all()
     serializer_class = BlockDeviceSerializer
     lookup_field = "pk"
 
@@ -154,7 +163,7 @@ class DeviceBlockAPIView(StaffEditorPermissionMixin, generics.UpdateAPIView):
 
 
 class DeviceDestroyAPIView(StaffEditorPermissionMixin, generics.DestroyAPIView):
-    queryset = Device.objects.all()
+    queryset = Device.objects.select_related("user").all()
     serializer_class = DeviceSerializer
     lookup_field = "pk"