Delay building arel relation as long as possible for improved introspection

1 files changed, 5 insertions, 9 deletions

diff --git a/activerecord/lib/active_record/relation/calculation_methods.rb b/activerecord/lib/active_record/relation/calculation_methods.rb
index 5246c7bc5d..e6f62ee49a 100644
--- a/activerecord/lib/active_record/relation/calculation_methods.rb
+++ b/activerecord/lib/active_record/relation/calculation_methods.rb
@@ -25,7 +25,7 @@ module ActiveRecord
       operation = operation.to_s.downcase
 
       if operation == "count"
-        joins = @relation.joins(relation)
+        joins = arel.joins(arel)
         if joins.present? && joins =~ /LEFT OUTER/i
           distinct = true
           column_name = @klass.primary_key if column_name == :all
@@ -40,7 +40,7 @@ module ActiveRecord
       distinct = options[:distinct] || distinct
       column_name = :all if column_name.blank? && operation == "count"
 
-      if @relation.send(:groupings).any?
+      if arel.send(:groupings).any?
         return execute_grouped_calculation(operation, column_name)
       else
         return execute_simple_calculation(operation, column_name, distinct)
@@ -63,7 +63,7 @@ module ActiveRecord
     end
 
     def execute_grouped_calculation(operation, column_name) #:nodoc:
-      group_attr      = @relation.send(:groupings).first.value
+      group_attr      = arel.send(:groupings).first.value
       association     = @klass.reflect_on_association(group_attr.to_sym)
       associated      = association && association.macro == :belongs_to # only count belongs_to associations
       group_field     = associated ? association.primary_key_name : group_attr
@@ -165,12 +165,8 @@ module ActiveRecord
       column ? column.type_cast(value) : value
     end
 
-    def get_projection_name_from_chained_relations(relation = @relation)
-      if relation.respond_to?(:projections) && relation.projections.present?
-        relation.send(:select_clauses).join(', ')
-      elsif relation.respond_to?(:relation)
-        get_projection_name_from_chained_relations(relation.relation)
-      end
+    def get_projection_name_from_chained_relations
+      @select_values.join(", ") if @select_values.present?
     end
 
   end