perf(Django): Use select_related to avoid N+1 queries (#403)

open_prices/api/prices/tests.py

@@ -35,11 +35,12 @@ def setUpTestData(cls):
 
     def test_price_list(self):
         # anonymous
-        response = self.client.get(self.url)
-        self.assertEqual(response.data["total"], 3)
-        self.assertEqual(len(response.data["items"]), 3)
-        self.assertTrue("id" in response.data["items"][0])
-        self.assertEqual(response.data["items"][0]["price"], 15.00)  # default order
+        with self.assertNumQueries(1 + 1):  # thanks to select_related
+            response = self.client.get(self.url)
+            self.assertEqual(response.data["total"], 3)
+            self.assertEqual(len(response.data["items"]), 3)
+            self.assertTrue("id" in response.data["items"][0])
+            self.assertEqual(response.data["items"][0]["price"], 15.00)  # default order
 
 
 class PriceListPaginationApiTest(TestCase):

open_prices/api/prices/views.py

@@ -32,7 +32,9 @@ class PriceViewSet(
     ordering = ["created"]
 
     def get_queryset(self):
-        if self.request.method in ["PATCH", "DELETE"]:
+        if self.request.method in ["GET"]:
+            return self.queryset.select_related("product", "location", "proof")
+        elif self.request.method in ["PATCH", "DELETE"]:
             # only return prices owned by the current user
             if self.request.user.is_authenticated:
                 return Price.objects.filter(owner=self.request.user.user_id)

open_prices/api/proofs/tests.py

@@ -1,6 +1,12 @@
+from django.db.models import signals
 from django.test import TestCase
 from django.urls import reverse
 
+from open_prices.locations import constants as location_constants
+from open_prices.locations.models import (
+    Location,
+    location_post_create_fetch_data_from_openstreetmap,
+)
 from open_prices.proofs import constants as proof_constants
 from open_prices.proofs.factories import ProofFactory
 from open_prices.proofs.models import Proof
@@ -20,6 +26,8 @@ def setUpTestData(cls):
         ProofFactory(price_count=0)
         ProofFactory(
             type=proof_constants.TYPE_PRICE_TAG,
+            location_osm_id=652825274,
+            location_osm_type=location_constants.OSM_TYPE_NODE,
             price_count=50,
             owner=cls.user_session.user.user_id,
         )
@@ -34,15 +42,16 @@ def test_proof_list(self):
         )
         self.assertEqual(response.status_code, 403)
         # authenticated
-        response = self.client.get(
-            self.url, headers={"Authorization": f"Bearer {self.user_session.token}"}
-        )
-        self.assertEqual(response.status_code, 200)
-        self.assertEqual(response.data["total"], 2)  # only user's proofs
-        self.assertEqual(len(response.data["items"]), 2)
-        self.assertEqual(
-            response.data["items"][0]["id"], self.proof.id
-        )  # default order
+        with self.assertNumQueries(4 + 1):  # thanks to select_related
+            response = self.client.get(
+                self.url, headers={"Authorization": f"Bearer {self.user_session.token}"}
+            )
+            self.assertEqual(response.status_code, 200)
+            self.assertEqual(response.data["total"], 2)  # only user's proofs
+            self.assertEqual(len(response.data["items"]), 2)
+            self.assertEqual(
+                response.data["items"][0]["id"], self.proof.id
+            )  # default order
 
 
 class ProofListOrderApiTest(TestCase):
@@ -129,6 +138,9 @@ def test_proof_detail(self):
 class ProofCreateApiTest(TestCase):
     @classmethod
     def setUpTestData(cls):
+        signals.post_save.disconnect(
+            location_post_create_fetch_data_from_openstreetmap, sender=Location
+        )
         cls.url = reverse("api:proofs-upload")
         cls.user_session = SessionFactory()
         cls.data = {

open_prices/api/proofs/views.py

@@ -38,7 +38,10 @@ class ProofViewSet(
     def get_queryset(self):
         # only return proofs owned by the current user
         if self.request.user.is_authenticated:
-            return Proof.objects.filter(owner=self.request.user.user_id)
+            queryset = Proof.objects.filter(owner=self.request.user.user_id)
+            if self.request.method in ["GET"]:
+                return queryset.select_related("location")
+            return queryset
         return self.queryset
 
     def get_serializer_class(self):