Calculate sum with SQL, not Enumerable on HasManyThrough Associations. [Dan Peterson]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@4640 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

3 files changed, 12 insertions, 1 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index 7900524a74..389de82445 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Calculate sum with SQL, not Enumerable on HasManyThrough Associations. [Dan Peterson]
+
 * Factor the attribute#{suffix} methods out of method_missing for easier extension. [Jeremy Kemper]
 
 * Patch sql injection vulnerability when using integer or float columns. [Jamis Buck]
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index c352a009d6..8f4ac104ad 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -47,7 +47,12 @@ module ActiveRecord
       [:push, :concat, :create, :build].each do |method|
         alias_method method, :<<
       end
-
+      
+      # Calculate sum using SQL, not Enumerable
+      def sum(*args, &block)
+        calculate(:sum, *args, &block)
+      end
+      
       protected
         def method_missing(method, *args, &block)
           if @target.respond_to?(method) || (!@reflection.klass.respond_to?(method) && Class.respond_to?(method))
diff --git a/activerecord/test/associations_join_model_test.rb b/activerecord/test/associations_join_model_test.rb
index ede21785e7..b5d48db8bc 100644
--- a/activerecord/test/associations_join_model_test.rb
+++ b/activerecord/test/associations_join_model_test.rb
@@ -370,6 +370,10 @@ class AssociationsJoinModelTest < Test::Unit::TestCase
     assert_raise(ActiveRecord::ReadOnlyAssociation) { posts(:thinking).tags.build(:name => 'foo')  }
     assert_raise(ActiveRecord::ReadOnlyAssociation) { posts(:thinking).tags.create(:name => 'foo') }
   end
+  
+  def test_has_many_through_sum_uses_calculations
+    assert_nothing_raised { authors(:david).comments.sum(:post_id) }
+  end
 
   private
     # create dynamic Post models to allow different dependency options