Optimize refresh_quota_caches for less long-running queries

src/pretix/base/services/quotas.py

@@ -1,11 +1,11 @@
 from datetime import timedelta
 
-from django.db import models
-from django.db.models import F, Max, OuterRef, Q, Subquery
+from django.conf import settings
+from django.db.models import Max, Q
 from django.dispatch import receiver
 from django.utils.timezone import now
 
-from pretix.base.models import LogEntry, Quota
+from pretix.base.models import Event, LogEntry
 from pretix.celery_app import app
 
 from ..signals import periodic_task
@@ -18,19 +18,25 @@ def build_all_quota_caches(sender, **kwargs):
 
 @app.task
 def refresh_quota_caches():
-    last_activity = LogEntry.objects.filter(
-        event=OuterRef('event_id'),
+    # Active events
+    active = LogEntry.objects.using(settings.DATABASE_REPLICA).filter(
+        datetime__gt=now() - timedelta(days=7)
     ).order_by().values('event').annotate(
-        m=Max('datetime')
-    ).values(
-        'm'
+        last_activity=Max('datetime')
     )
-    quotas = Quota.objects.annotate(
-        last_activity=Subquery(last_activity, output_field=models.DateTimeField())
-    ).filter(
-        Q(cached_availability_time__isnull=True) |
-        Q(cached_availability_time__lt=F('last_activity')) |
-        Q(cached_availability_time__lt=now() - timedelta(hours=2), last_activity__gt=now() - timedelta(days=7))
-    ).select_related('subevent')
-    for q in quotas:
-        q.availability()
+    for a in active:
+        try:
+            e = Event.objects.using(settings.DATABASE_REPLICA).get(pk=a['event'])
+        except Event.DoesNotExist:
+            continue
+        quotas = e.quotas.filter(
+            Q(cached_availability_time__isnull=True) |
+            Q(cached_availability_time__lt=a['last_activity']) |
+            Q(cached_availability_time__lt=now() - timedelta(hours=2))
+        ).filter(
+            Q(subevent__isnull=True) |
+            Q(subevent__date_to__isnull=False, subevent__date_to__gte=now() - timedelta(days=14)) |
+            Q(subevent__date_from__gte=now() - timedelta(days=14))
+        )
+        for q in quotas:
+            q.availability()