Add missing index on country of subdivision

country.py

@@ -52,7 +52,7 @@ class Subdivision(ModelSQL, ModelView):
     _name = 'country.subdivision'
     _description = __doc__
     country = fields.Many2One('country.country', 'Country',
-            required=True)
+            required=True, select=1)
     name = fields.Char('Name', required=True, select=1)
     code = fields.Char('Code', required=True, select=1)
     type = fields.Selection([