Optimize recent votes admin query

helios/stats_views.py

@@ -6,7 +6,7 @@
 
 from django.core.paginator import Paginator
 from django.urls import reverse
-from django.db.models import Max, Count
+from django.db.models import Max, Count, Q
 from django.http import HttpResponseRedirect
 from django.views.decorators.http import require_http_methods
 
@@ -56,10 +56,16 @@ def elections(request):
 
 def recent_votes(request):
   user = require_admin(request)
-  
+
   # elections with a vote in the last 24 hours, ordered by most recent cast vote time
   # also annotated with number of votes cast in last 24 hours
-  elections_with_votes_in_24hours = Election.objects.filter(voter__castvote__cast_at__gt= datetime.datetime.utcnow() - datetime.timedelta(days=1)).annotate(last_cast_vote = Max('voter__castvote__cast_at'), num_recent_cast_votes = Count('voter__castvote')).order_by('-last_cast_vote')
+  cutoff = datetime.datetime.utcnow() - datetime.timedelta(days=1)
+  elections_with_votes_in_24hours = Election.objects.filter(
+    voter__castvote__cast_at__gt=cutoff
+  ).distinct().annotate(
+    last_cast_vote=Max('voter__castvote__cast_at', filter=Q(voter__castvote__cast_at__gt=cutoff)),
+    num_recent_cast_votes=Count('voter__castvote', filter=Q(voter__castvote__cast_at__gt=cutoff))
+  ).order_by('-last_cast_vote')
 
   return render_template(request, "stats_recent_votes", {'elections' : elections_with_votes_in_24hours})