Optimization of UserPagePermissionsProxy.revisions_for_moderation (#5311)

revisions_for_moderation() was iterating over Page instances only
to use their path attribute. The optimization uses values_list()
over the GroupPagePermission queryset to retrieve only the page
paths without having to create the model instances in memory. This
saves roughly 50% of the runtime.

CHANGELOG.txt

@@ -25,6 +25,7 @@ Changelog
  * Added support for custom search handler classes to modeladmin's IndexView, and added a class that uses the default Wagtail search backend for searching (Seb Brown, Andy Babic)
  * Improved heading structure for screen reader users navigating the CMS admin (Beth Menzies, Helen Chapman)
  * Updated group edit view to expose the Permission object for each checkbox (George Hickman)
+ * Improve performance of Pages for Moderation panel (Fidel Ramos)
  * Fix: ModelAdmin no longer fails when filtering over a foreign key relation (Jason Dilworth, Matt Westcott)
  * Fix: The Wagtail version number is now visible within the Settings menu (Kevin Howbrook)
  * Fix: Scaling images now rounds values to an integer so that images render without errors (Adrian Brunyate)

CONTRIBUTORS.rst

@@ -378,6 +378,7 @@ Contributors
 * George Hickman
 * Eric Dyken
 * Jordan Bauer
+* Fidel Ramos
 
 Translators
 ===========

docs/releases/2.6.rst

@@ -34,6 +34,7 @@ Other features
  * Added support for custom search handler classes to modeladmin's IndexView, and added a class that uses the default Wagtail search backend for searching (Seb Brown, Andy Babic)
  * Improved heading structure for screen reader users navigating the CMS admin (Beth Menzies, Helen Chapman)
  * Update group edit view to expose the ``Permission`` object for each checkbox (George Hickman)
+ * Improve performance of Pages for Moderation panel (Fidel Ramos)
 
 
 Bug fixes

wagtail/core/models.py

@@ -1623,15 +1623,17 @@ class UserPagePermissionsProxy:
 
         # get the list of pages for which they have direct publish permission
         # (i.e. they can publish any page within this subtree)
-        publishable_pages = [perm.page for perm in self.permissions if perm.permission_type == 'publish']
-        if not publishable_pages:
+        publishable_pages_paths = self.permissions.filter(
+            permission_type='publish'
+        ).values_list('page__path', flat=True).distinct()
+        if not publishable_pages_paths:
             return PageRevision.objects.none()
 
         # compile a filter expression to apply to the PageRevision.submitted_revisions manager:
         # return only those pages whose paths start with one of the publishable_pages paths
-        only_my_sections = Q(page__path__startswith=publishable_pages[0].path)
-        for page in publishable_pages[1:]:
-            only_my_sections = only_my_sections | Q(page__path__startswith=page.path)
+        only_my_sections = Q(page__path__startswith=publishable_pages_paths[0])
+        for page_path in publishable_pages_paths[1:]:
+            only_my_sections = only_my_sections | Q(page__path__startswith=page_path)
 
         # return the filtered queryset
         return PageRevision.submitted_revisions.filter(only_my_sections)