Make ical feed generation of meetings not slow

The lookup for participating was very expensive and slow. It would cause
timeouts so some users' calendars would not load.

lego/apps/events/permissions.py

@@ -9,7 +9,7 @@
 log = get_logger()
 
 
-class EventPermissionHandler(PermissionHandler):
+class EventPermissionHandler(PermissionHandler["Event"]):
     perms_without_object = [CREATE, "administrate"]
 
     def event_type_keyword_permissions(self, event_type, perm):

lego/apps/ical/utils.py

@@ -59,7 +59,8 @@ def add_meeting_to_ical_feed(feed, meeting, user):
         start_datetime=meeting.start_time,
         end_datetime=meeting.end_time,
         location=meeting.location,
-        transparency="OPAQUE" if user in meeting.participants else "TRANSPARENT",
+        # This uses an annotation on the queryset for performance reasons
+        transparency="OPAQUE" if meeting.user_participating else "TRANSPARENT",
     )
 
 

lego/apps/ical/viewsets.py

@@ -1,5 +1,6 @@
 from datetime import timedelta
 
+from django.db import FilteredRelation, Q
 from django.utils import timezone
 from rest_framework import decorators, permissions, viewsets
 from rest_framework.permissions import IsAuthenticated
@@ -92,7 +93,16 @@ def personal(self, request):
         )
 
         permission_handler = get_permission_handler(Meeting)
-        meetings = permission_handler.filter_queryset(request.user, Meeting.objects)
+        meetings = permission_handler.filter_queryset(
+            request.user,
+            Meeting.objects.annotate(
+                # Annotate the queryset with participating status for use in the feed generation.
+                # Otherwise lookups are very expensive
+                user_participating=FilteredRelation(
+                    "participants", condition=Q(participants__in=request.user)
+                )
+            ),
+        )
 
         utils.add_events_to_ical_feed(feed, following_events)
         utils.add_meetings_to_ical_feed(feed, meetings, request.user)

lego/apps/permissions/permissions.py

@@ -1,14 +1,22 @@
-from django.db.models import Q
+from typing import TYPE_CHECKING, Generic, TypeVar
+
+from django.db.models import Q, QuerySet
 
 from lego.apps.permissions.constants import CREATE, LIST, VIEW
 from lego.apps.permissions.models import ObjectPermissionsModel
 
+if TYPE_CHECKING:
+    from lego.apps.users.models import User
+
 
 def _check_intersection(first, second):
     return len(set(first).intersection(set(second))) > 0
 
 
-class PermissionHandler:
+T = TypeVar("T")
+
+
+class PermissionHandler(Generic[T]):
     """
     The permission handler defines how permissions should be handled on a model
 
@@ -161,7 +169,9 @@ def has_perm(
 
         return False
 
-    def filter_queryset(self, user, queryset, **kwargs):
+    def filter_queryset(
+        self, user: User, queryset: QuerySet[T], **kwargs
+    ) -> QuerySet[T]:
         """
         Filter queryset based on object-level permissions.
         We currently only supports queryset filtering on ObjectPermissionsModels.

lego/apps/permissions/utils.py

@@ -1,11 +1,16 @@
+from typing import TypeVar
+
 from lego.apps.permissions.permissions import PermissionHandler
 
 # isort:skip
 
 default_permission_handler = PermissionHandler()
 
 
-def get_permission_handler(model):
+T = TypeVar("T")
+
+
+def get_permission_handler(model: T) -> PermissionHandler[T]:
     """
     Try to get the permission handler used by the model or use the default handler.
     """