[RFC] admin: prefetch related fields

pinax/stripe/admin.py

@@ -1,4 +1,5 @@
 from django.contrib import admin
+from django.contrib.admin.views.main import ChangeList
 from django.contrib.auth import get_user_model
 from django.db.models import Count
 
@@ -103,8 +104,28 @@ def queryset(self, request, queryset):
         return queryset.all()
 
 
+class PrefetchingChangeList(ChangeList):
+    """A custom changelist to prefetch related fields."""
+    def get_queryset(self, request):
+        qs = super(PrefetchingChangeList, self).get_queryset(request)
+
+        if subscription_status in self.list_display:
+            qs = qs.prefetch_related("subscription_set")
+        if "customer" in self.list_display:
+            qs = qs.prefetch_related("customer")
+        if "user" in self.list_display:
+            qs = qs.prefetch_related("user")
+        return qs
+
+
+class ModelAdmin(admin.ModelAdmin):
+    def get_changelist(self, request, **kwargs):
+        return PrefetchingChangeList
+
+
 admin.site.register(
     Charge,
+    admin_class=ModelAdmin,
     list_display=[
         "stripe_id",
         "customer",
@@ -200,6 +221,7 @@ def subscription_status(obj):
 
 admin.site.register(
     Customer,
+    admin_class=ModelAdmin,
     raw_id_fields=["user"],
     list_display=[
         "stripe_id",

pinax/stripe/tests/test_admin.py

@@ -1,5 +1,6 @@
 import datetime
 
+import django
 from django.contrib.auth import get_user_model
 from django.test import Client, TestCase
 from django.utils import timezone
@@ -99,8 +100,16 @@ def setUp(self):
     def test_customer_admin(self):
         """Make sure we get good responses for all filter options"""
         url = reverse("admin:pinax_stripe_customer_changelist")
-        response = self.client.get(url)
-        self.assertEqual(response.status_code, 200)
+
+        # Django 1.10 has the following query twice:
+        # SELECT COUNT(*) AS "__count" FROM "pinax_stripe_customer"
+        # (since https://github.com/django/django/commit/5fa7b592b3f)
+        # We might want to test for "num < 10" here instead, and/or compare the
+        # number to be equal with X and X+1 customers
+        num = 8 if django.VERSION >= (1, 10) else 7
+        with self.assertNumQueries(num):
+            response = self.client.get(url)
+            self.assertEqual(response.status_code, 200)
 
         response = self.client.get(url + "?sub_status=active")
         self.assertEqual(response.status_code, 200)