Remove workaround for inefficient query planning

We have migrated MapIt to use Postgres 9.6 and PostGIS 2.3 now; Matthew
Somerville investigated whether this sub-optimal query planning still
happens with those versions, but it doesn't seem to. The query time is
considerably faster as well. So, we believe that this workaround should
no longer be necessary, but this commit should revert cleanly if in
practice we discover the problem is still present with some other
variant of these queries or data.

mapit/views/areas.py

@@ -12,7 +12,7 @@
 from django.shortcuts import redirect, render
 from django.views.decorators.csrf import csrf_exempt
 
-from mapit.models import Area, Generation, Geometry, Code, Name
+from mapit.models import Area, Generation, Code, Name
 from mapit.shortcuts import output_json, output_html, output_polygon, get_object_or_404, set_timeout
 from mapit.middleware import ViewException
 from mapit.ratelimitcache import ratelimit
@@ -363,30 +363,12 @@ def areas_by_point(request, srid, x, y, bb=False, format='json'):
     method = 'box' if bb and bb != 'polygon' else 'polygon'
 
     args = query_args(request, format)
-    type = request.GET.get('type', '')
-    country = request.GET.get('country', '')
-
-    if (type or country) and method == 'polygon':
-        args = dict(("area__%s" % k, v) for k, v in args.items())
-        # So this is odd. It doesn't matter if you specify types, PostGIS will
-        # do the contains test on all the geometries matching the bounding-box
-        # index, even if it could be much quicker to filter some out first
-        # (ie. the EUR ones).
-        args['polygon__bbcontains'] = location
-        shapes = Geometry.objects.filter(**args).defer('polygon')
-        areas = []
-        for shape in shapes:
-            try:
-                areas.append(Area.objects.get(polygons__id=shape.id, polygons__polygon__contains=location))
-            except:
-                pass
+
+    if method == 'box':
+        args['polygons__polygon__bbcontains'] = location
     else:
-        if method == 'box':
-            args['polygons__polygon__bbcontains'] = location
-        else:
-            geoms = list(Geometry.objects.filter(polygon__contains=location).defer('polygon'))
-            args['polygons__in'] = geoms
-        areas = Area.objects.filter(**args)
+        args['polygons__polygon__contains'] = location
+    areas = Area.objects.filter(**args)
 
     return output_areas(
         request, _('Areas covering the point ({0},{1})').format(x, y),