optimizing database requests

cfp/models.py

@@ -63,6 +63,17 @@ class Conference(models.Model):
         return str(self.site)
 
 
+class ParticipantManager(models.Manager):
+    def get_queryset(self):
+        qs = super().get_queryset()
+        qs = qs.annotate(
+            accepted_talk_count=models.Sum(models.Case(models.When(talk__accepted=True, then=1), default=0, output_field=models.IntegerField())),
+            pending_talk_count=models.Sum(models.Case(models.When(talk__accepted=None, then=1), default=0, output_field=models.IntegerField())),
+            refused_talk_count=models.Sum(models.Case(models.When(talk__accepted=False, then=1), default=0, output_field=models.IntegerField())),
+        )
+        return qs
+
+
 class Participant(PonyConfModel):
 
     site = models.ForeignKey(Site, on_delete=models.CASCADE)
@@ -90,6 +101,8 @@ class Participant(PonyConfModel):
 
     conversation = models.OneToOneField(MessageThread)
 
+    objects = ParticipantManager()
+
     class Meta:
         # A User can participe only once to a Conference (= Site)
         unique_together = ('site', 'email')

cfp/templates/cfp/staff/participant_list.html

@@ -65,11 +65,11 @@
         <tr>
             <td><a href="{% url 'participant-details' participant.token %}">{{ participant }}</a></td>
             <td>
-                <span class="text-success">{% blocktrans count accepted=participant.accepted_talk_set.count %}accepted: {{ accepted }}{% plural %}accepted: {{ accepted }}{% endblocktrans %}</span>
+                <span class="text-success">{% blocktrans count accepted=participant.accepted_talk_count %}accepted: {{ accepted }}{% plural %}accepted: {{ accepted }}{% endblocktrans %}</span>
                 —
-                <span class="text-warning">{% blocktrans count pending=participant.pending_talk_set.count %}pending: {{ pending }}{% plural %}pending: {{ pending }}{% endblocktrans %}</span>
+                <span class="text-warning">{% blocktrans count pending=participant.pending_talk_count %}pending: {{ pending }}{% plural %}pending: {{ pending }}{% endblocktrans %}</span>
                 —
-                <span class="text-danger">{% blocktrans count refused=participant.refused_talk_set.count %}refused: {{ refused }}{% plural %}refused: {{ refused }}{% endblocktrans %}</span>
+                <span class="text-danger">{% blocktrans count refused=participant.refused_talk_count %}refused: {{ refused }}{% plural %}refused: {{ refused }}{% endblocktrans %}</span>
             </td>
             {% comment %}
             <td>

cfp/views.py

@@ -195,7 +195,7 @@ def talk_list(request, conference):
             glyphicon = 'sort'
         sort_urls[c] = url.urlencode()
         sort_glyphicons[c] = glyphicon
-    talks = talks.prefetch_related('speakers')
+    talks = talks.prefetch_related('category', 'speakers')
     return render(request, 'cfp/staff/talk_list.html', {
         'show_filters': show_filters,
         'talk_list': talks,