Make sure any Fixnum returned by a DB sum is type cast to a Float before...

Make sure any Fixnum returned by a DB sum is type cast to a Float before standard converstion to a BigDecimal [#8994 state:resolved]
Signed-off-by: NJoshua Peek <josh@joshpeek.com>

activerecord/lib/active_record/calculations.rb

@@ -286,7 +286,7 @@ def type_cast_calculated_value(value, column, operation = nil)
           case operation
             when 'count' then value.to_i
             when 'sum'   then type_cast_using_column(value || '0', column)
-            when 'avg'   then value && (value == 0 ? 0.0.to_d : value.to_d)
+            when 'avg'   then value && (value.is_a?(Fixnum) ? value.to_f : value).to_d
             else type_cast_using_column(value, column)
           end
         end

activerecord/test/cases/calculations_test.rb

@@ -25,6 +25,11 @@ def test_should_average_field
   def test_should_return_nil_as_average
     assert_nil NumericData.average(:bank_balance)
   end
+  
+  def test_type_cast_calculated_value_should_convert_db_averages_of_fixnum_class_to_decimal
+    assert_equal 0, NumericData.send(:type_cast_calculated_value, 0, nil, 'avg')
+    assert_equal 53.0, NumericData.send(:type_cast_calculated_value, 53, nil, 'avg')
+  end
 
   def test_should_get_maximum_of_field
     assert_equal 60, Account.maximum(:credit_limit)