Event: Fixes the N+1 query by dropping eagerly loading on the unused relationships in the iCal export

TYPE: Performance
LINK: https://seantis-gmbh.sentry.io/issues/7605741267

Author: Tschuppi81

src/onegov/event/collections/occurrences.py

@@ -18,6 +18,7 @@
 from sqlalchemy.dialects.postgresql import array
 from sqlalchemy.orm import contains_eager
 from sqlalchemy.orm import joinedload
+from sqlalchemy.orm import raiseload
 from sqlalchemy.orm import undefer
 from webob.multidict import MultiDict
 
@@ -772,6 +773,11 @@ def as_ical(self, request: CoreRequest) -> bytes:
 
         query = self.session.query(Event).filter(Event.id.in_(event_ids))
         query = query.options(undefer(Event.content))
+        # raise instead of eager-loading relations get_ical_vevents won't use
+        query = query.options(
+            raiseload(Event.occurrences),
+            raiseload(Event.filter_keyword_objects),
+        )
         for event in query:
             for vevent in event.get_ical_vevents(request.link(event)):
                 vcalendar.add_component(vevent)