performance: grid view (157 -> 12 queries)

panikweb/views.py

@@ -210,7 +210,8 @@ class Grid(TemplateView):
                     time_cell.time_label = '%02d:00-%02d:00' % (
                             nonstop[0], nonstop[1])
 
-        for schedule in Schedule.objects.select_related().order_by('datetime'):
+        for schedule in Schedule.objects.prefetch_related(
+                'emission__categories').select_related().order_by('datetime'):
             row_start = schedule.datetime.hour * 2 + \
                     int(math.ceil(schedule.datetime.minute / 30))
             day_no = schedule.get_weekday()