Confirm Lab 2.1 problem.

Author: tim-schilling

project/tests/test_lab2_1.py

@@ -0,0 +1,62 @@
+from django.contrib.auth.models import User
+from django.test import Client, TestCase, tag
+from django.urls import reverse
+
+from project.newsletter.models import Category, Post
+
+
+@tag("lab_test")
+class TestAdminListViewNPlusOne(TestCase):
+    def test_verify_broken(self):
+        author = User.objects.create_superuser(username="u1")
+        categories = [
+            Category.objects.create(slug=f"c{i}", title=f"Cat {i}") for i in range(5)
+        ]
+        for i in range(5):
+            post = Post.objects.create(
+                author=author, slug=f"post{i}", title=f"Post {i}"
+            )
+            post.categories.set(categories)
+        client = Client()
+        client.force_login(author)
+
+        with self.assertNumQueries(11):
+            # This should contain duplicate queries on category
+            client.get("/admin/newsletter/post/")
+
+
+@tag("lab_test")
+class TestListViewsCategoriesNPlusOne(TestCase):
+    def setUp(self) -> None:
+        author = User.objects.create_superuser(username="u1")
+        categories = [
+            Category.objects.create(slug=f"c{i}", title=f"Cat {i}") for i in range(5)
+        ]
+        for i in range(5):
+            post = Post.objects.create(
+                author=author,
+                slug=f"post{i}",
+                title=f"Post {i}",
+                is_public=True,
+                is_published=True,
+            )
+            post.categories.set(categories)
+        self.client = Client()
+        self.client.force_login(author)
+
+    def test_list_posts(self):
+        with self.assertNumQueries(9):
+            # This should contain duplicate queries on category
+            self.client.get(reverse("newsletter:list_posts"))
+
+    def test_landing(self):
+        with self.assertNumQueries(7):
+            # This should contain duplicate queries on category
+            self.client.get(reverse("newsletter:landing"))
+
+
+@tag("lab_test")
+class TestPostSlugMissingIndex(TestCase):
+    def test_sql_uses_scan_without_index(self):
+        self.assertIn("scan", Post.objects.filter(slug="test").explain().lower())
+        self.assertNotIn("index", Post.objects.filter(slug="test").explain().lower())