[devel][forwardport] AAP-83773 — Use unfiltered count for activity stream pagination (#16557)

* AAP-83773 — Use unfiltered count for activity stream pagination

Forward-port of tower#7606 (stable-2.6).

The RBAC-filtered COUNT(*) on activity_stream takes ~36 min per call
on large tables (713K rows) due to the pk__in subquery shape introduced
by the AAP-81860 LEFT JOIN fix.  Replace with an unfiltered table count
for pagination -- an approximate over-count is harmless for UI page
navigation while the actual page results remain RBAC-filtered.

* AAP-83773 — Add unit tests for ActivityStreamPagination

Cover ActivityStreamPaginator and ActivityStreamPagination to satisfy
SonarCloud coverage gate on new lines in awx/api/pagination.py.

* AAP-83773 — Save/restore django_paginator_class in base Pagination

Address review feedback from lallen92: use a save/restore pattern in
Pagination.paginate_queryset() so subclasses only need to set the class
attribute. Remove the now-redundant paginate_queryset override from
ActivityStreamPagination.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: Liam Allen <lallen@redhat.com>

awx/api/pagination.py

@@ -6,12 +6,15 @@ from collections import OrderedDict
 # Django REST Framework
 from django.conf import settings
 from django.core.paginator import Paginator as DjangoPaginator
+from django.utils.functional import cached_property
 from rest_framework import pagination
 from rest_framework.response import Response
 from rest_framework.utils.urls import replace_query_param
 from rest_framework.settings import api_settings
 from django.utils.translation import gettext_lazy as _
 
+from awx.main.models import ActivityStream
+
 
 class DisabledPaginator(DjangoPaginator):
     @property
@@ -23,6 +26,19 @@ class DisabledPaginator(DjangoPaginator):
         return 200
 
 
+class ActivityStreamPaginator(DjangoPaginator):
+    """Use unfiltered table count for activity stream pagination (AAP-83773).
+
+    The RBAC-filtered COUNT query takes ~36 min on large tables due to the
+    pk__in subquery shape from AAP-81860.  An unfiltered count is acceptable
+    for pagination UI -- an approximate over-count is harmless.
+    """
+
+    @cached_property
+    def count(self):
+        return ActivityStream.objects.count()
+
+
 class Pagination(pagination.PageNumberPagination):
     page_size_query_param = 'page_size'
     max_page_size = settings.MAX_PAGE_SIZE
@@ -57,12 +73,13 @@ class Pagination(pagination.PageNumberPagination):
 
     def paginate_queryset(self, queryset, request, **kwargs):
         self.count_disabled = 'count_disabled' in request.query_params
+        original_paginator = self.django_paginator_class
         try:
             if self.count_disabled:
                 self.django_paginator_class = DisabledPaginator
             return super(Pagination, self).paginate_queryset(queryset, request, **kwargs)
         finally:
-            self.django_paginator_class = DjangoPaginator
+            self.django_paginator_class = original_paginator
 
     def get_paginated_response(self, data):
         if self.count_disabled:
@@ -70,6 +87,10 @@ class Pagination(pagination.PageNumberPagination):
         return super(Pagination, self).get_paginated_response(data)
 
 
+class ActivityStreamPagination(Pagination):
+    django_paginator_class = ActivityStreamPaginator
+
+
 class LimitPagination(pagination.BasePagination):
     default_limit = api_settings.PAGE_SIZE
     limit_query_param = 'limit'

awx/api/views/__init__.py

@@ -129,7 +129,7 @@ from awx.api.views.mixin import (
     NoTruncateMixin,
     UnifiedJobExcludeMixin,
 )
-from awx.api.pagination import UnifiedJobEventPagination
+from awx.api.pagination import ActivityStreamPagination, UnifiedJobEventPagination
 from awx.main.utils import set_environ
 
 logger = logging.getLogger('awx.api.views')
@@ -4818,6 +4818,7 @@ class ActivityStreamList(SimpleListAPIView):
     model = models.ActivityStream
     serializer_class = serializers.ActivityStreamSerializer
     search_fields = ('changes',)
+    pagination_class = ActivityStreamPagination
     resource_purpose = 'audit trail entries for tracking system changes'
 
     @extend_schema_if_available(