core/applications: Optimize list applications when only_with_launch_url=true (#20428)

* Performance optimizations for the application list API endpoint when only_with_launch_url=true

* lint

---------

Signed-off-by: Simonyi Gergő <28359278+gergosimonyi@users.noreply.github.com>
Co-authored-by: Simonyi Gergő <28359278+gergosimonyi@users.noreply.github.com>

authentik/core/api/applications.py

@@ -4,7 +4,7 @@ from collections.abc import Iterator
 from copy import copy
 
 from django.core.cache import cache
-from django.db.models import Case, QuerySet
+from django.db.models import Case, Q, QuerySet
 from django.db.models.expressions import When
 from django.shortcuts import get_object_or_404
 from django.utils.translation import gettext as _
@@ -36,9 +36,13 @@ from authentik.rbac.filters import ObjectFilter
 LOGGER = get_logger()
 
 
-def user_app_cache_key(user_pk: str, page_number: int | None = None) -> str:
+def user_app_cache_key(
+    user_pk: str, page_number: int | None = None, only_with_launch_url: bool = False
+) -> str:
     """Cache key where application list for user is saved"""
     key = f"{CACHE_PREFIX}app_access/{user_pk}"
+    if only_with_launch_url:
+        key += "/launch"
     if page_number:
         key += f"/{page_number}"
     return key
@@ -279,6 +283,14 @@ class ApplicationViewSet(UsedByMixin, ModelViewSet):
         ).lower()
 
         queryset = self._filter_queryset_for_list(self.get_queryset())
+        if only_with_launch_url == "true":
+            # Pre-filter at DB level to skip expensive per-app policy evaluation
+            # for apps that can never appear in the launcher:
+            # - No meta_launch_url AND no provider: no possible launch URL
+            # - meta_launch_url="blank://blank": documented convention to hide from launcher
+            queryset = queryset.exclude(
+                Q(meta_launch_url="", provider__isnull=True) | Q(meta_launch_url="blank://blank")
+            )
         paginator: Pagination = self.paginator
         paginated_apps = paginator.paginate_queryset(queryset, request)
 
@@ -295,7 +307,6 @@ class ApplicationViewSet(UsedByMixin, ModelViewSet):
             except ValueError as exc:
                 raise ValidationError from exc
             allowed_applications = self._get_allowed_applications(paginated_apps, user=for_user)
-            allowed_applications = self._expand_applications(allowed_applications)
 
             serializer = self.get_serializer(allowed_applications, many=True)
             return self.get_paginated_response(serializer.data)
@@ -305,17 +316,24 @@ class ApplicationViewSet(UsedByMixin, ModelViewSet):
             allowed_applications = self._get_allowed_applications(paginated_apps)
         if should_cache:
             allowed_applications = cache.get(
-                user_app_cache_key(self.request.user.pk, paginator.page.number)
+                user_app_cache_key(
+                    self.request.user.pk, paginator.page.number, only_with_launch_url == "true"
                 )
-            if not allowed_applications:
+            )
+            if allowed_applications:
+                # Re-fetch cached applications since pickled instances lose prefetched
+                # relationships, causing N+1 queries during serialization
+                allowed_applications = self._expand_applications(allowed_applications)
+            else:
                 LOGGER.debug("Caching allowed application list", page=paginator.page.number)
                 allowed_applications = self._get_allowed_applications(paginated_apps)
                 cache.set(
-                    user_app_cache_key(self.request.user.pk, paginator.page.number),
+                    user_app_cache_key(
+                        self.request.user.pk, paginator.page.number, only_with_launch_url == "true"
+                    ),
                     allowed_applications,
                     timeout=86400,
                 )
-        allowed_applications = self._expand_applications(allowed_applications)
 
         if only_with_launch_url == "true":
             allowed_applications = self._filter_applications_with_launch_url(allowed_applications)

authentik/core/models.py

@@ -790,9 +790,13 @@ class Application(SerializerModel, PolicyBindingModel):
 
     def get_provider(self) -> Provider | None:
         """Get casted provider instance. Needs Application queryset with_provider"""
+        if hasattr(self, "_cached_provider"):
+            return self._cached_provider
         if not self.provider:
+            self._cached_provider = None
             return None
-        return get_deepest_child(self.provider)
+        self._cached_provider = get_deepest_child(self.provider)
+        return self._cached_provider
 
     def backchannel_provider_for[T: Provider](self, provider_type: type[T], **kwargs) -> T | None:
         """Get Backchannel provider for a specific type"""