Show only countries from the current year by default

We were fetching all events from the DB before, to show a list of
countries. That's pretty slow. We now do this only if the "Show past
events" option is selected by the user.

The method still needs to be optimized a lot, since it loads all events,
then traverses them in the code just to fetch their countries.

web/processors/event.py

@@ -45,10 +45,11 @@ def list_countries():
     return all_countries
 
 
-def list_active_countries():
+def list_active_countries(with_past_events=False):
     """ List countries with at least an Event associated """
+    start_year = 2014 if with_past_events else datetime.datetime.now().year
     events_countries = Event.objects.filter(
-            start_date__gte=datetime.date(2014, 1, 1),
+            start_date__gte=datetime.date(start_year, 1, 1),
             status='APPROVED'
         ).only('country').distinct()
 

web/views/events.py

@@ -71,7 +71,7 @@ def index(request):
         lan_lon = (58.08695, 5.58121)
 
     ambassadors = get_ambassadors(country['country_code'])
-    all_countries = list_active_countries()
+    all_countries = list_active_countries(with_past_events=(past == 'yes'))
 
     return render_to_response(
         template, {