ActiveRecord::Base#sum defaults to 0 if no rows are returned. Closes #11550 [kamal]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@9243 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* ActiveRecord::Base#sum defaults to 0 if no rows are returned.  Closes #11550 [kamal]
+
 * Ensure that respond_to? considers dynamic finder methods. Closes #11538. [floehopper]
 
 * Ensure that save on parent object fails for invalid has_one association. Closes #10518. [Pratik]

activerecord/lib/active_record/calculations.rb

@@ -71,7 +71,7 @@ def maximum(column_name, options = {})
       #
       #   Person.sum('age')
       def sum(column_name, options = {})
-        calculate(:sum, column_name, options)
+        calculate(:sum, column_name, options) || 0
       end
 
       # This calculates aggregate values in the given column.  Methods for count, sum, average, minimum, and maximum have been added as shortcuts.

activerecord/test/cases/calculations_test.rb

@@ -97,6 +97,10 @@ def test_should_sum_field_with_conditions
     assert_equal 105, Account.sum(:credit_limit, :conditions => 'firm_id = 6')
   end
 
+  def test_should_return_zero_if_sum_conditions_return_nothing
+    assert_equal 0, Account.sum(:credit_limit, :conditions => '1 = 2')
+  end
+
   def test_should_group_by_summed_field_with_conditions
     c = Account.sum(:credit_limit, :conditions => 'firm_id > 1',
                                    :group => :firm_id)