refactoring to remove crazy logic

activerecord/lib/active_record/relation/calculations.rb

@@ -191,7 +191,11 @@ module ActiveRecord
       end
 
       # Postgresql doesn't like ORDER BY when there are no GROUP BY
-      relation = except(:order).select(operation == 'count' ? column.count(distinct) : column.send(operation))
+      relation = except(:order)
+      select_value = operation == 'count' ? column.count(distinct) : column.send(operation)
+
+      relation.select_values = [select_value]
+
       type_cast_calculated_value(@klass.connection.select_value(relation.to_sql), column_for(column_name), operation)
     end
 

activerecord/lib/active_record/relation/query_methods.rb

@@ -259,14 +259,7 @@ module ActiveRecord
     def build_select(arel, selects)
       unless selects.empty?
         @implicit_readonly = false
-        # TODO: fix this ugly hack, we should refactor the callers to get an Arel compatible array.
-        # Before this change we were passing to Arel the last element only, and Arel is capable of handling an array
-        case select = selects.last
-        when Arel::Expression, Arel::SqlLiteral
-          arel.project(select)
-        else
-          arel.project(*selects)
-        end
+        arel.project(*selects)
       else
         arel.project(Arel::SqlLiteral.new(@klass.quoted_table_name + '.*'))
       end