Improve cache utilization of pagination

isic/core/pagination.py

@@ -125,7 +125,8 @@ def paginate_queryset(
         # If we have an offset cursor then offset the entire page by that amount.
         # We also always fetch an extra item in order to determine if there is a
         # page following on from this one.
-        results = list(queryset[cursor.offset : cursor.offset + limit + 1])
+        # Always fetch the maximum page size to increase cache utilization.
+        results = list(queryset[cursor.offset : cursor.offset + self.max_page_size + 1])
         page = list(results[:limit])
 
         # Determine the position of the final item following the page.

isic/ingest/tests/test_api_pagination.py

@@ -38,3 +38,27 @@ def test_pagination(image_factory, staff_client):
     assert len(resp.json()["results"]) == 1
     assert resp.json()["results"][0]["isic_id"] == images[1].isic_id
     assert resp.json()["previous"] is None
+
+
+@pytest.fixture()
+def _local_memory_cache(settings):
+    settings.CACHES = {
+        "default": {
+            "BACKEND": "django.core.cache.backends.locmem.LocMemCache",
+        }
+    }
+
+
+@pytest.mark.django_db()
+@pytest.mark.usefixtures("_local_memory_cache")
+def test_pagination_caches_correctly(image_factory, client, django_assert_num_queries):
+    for _ in range(2):
+        image_factory(public=True)
+
+    # one query for the count and the other for the values
+    with django_assert_num_queries(2):
+        resp_1 = client.get("/api/v2/images/", data={"limit": 1})
+        resp_2 = client.get("/api/v2/images/", data={"limit": 2})
+
+    assert resp_1.status_code == 200, resp_1.json()
+    assert resp_2.status_code == 200, resp_2.json()