Optimise queries in page listing views by prefetching workflow states of the parent page

wagtail/admin/tests/pages/test_explorer_view.py

@@ -796,7 +796,7 @@ class TestInWorkflowStatus(WagtailTestUtils, TestCase):
         # Warm up cache
         self.client.get(self.url)
 
-        with self.assertNumQueries(50):
+        with self.assertNumQueries(47):
             response = self.client.get(self.url)
 
         self.assertEqual(response.status_code, 200)

wagtail/admin/views/pages/listing.py

@@ -73,7 +73,9 @@ class IndexView(PermissionCheckedMixin, BaseListingView):
 
     def get(self, request, parent_page_id=None):
         if parent_page_id:
-            self.parent_page = get_object_or_404(Page, id=parent_page_id)
+            self.parent_page = get_object_or_404(
+                Page.objects.all().prefetch_workflow_states(), id=parent_page_id
+            )
         else:
             self.parent_page = Page.get_first_root_node()