Serialized attributes should only be saved with partial_updates when the serialized attribute is present [#2397 state:resolved]

Signed-off-by: Pratik Naik <pratiknaik@gmail.com>

2 files changed, 11 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index 9ec1fbeee1..911c908c8b 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -161,7 +161,7 @@ module ActiveRecord
           if partial_updates?
             # Serialized attributes should always be written in case they've been
             # changed in place.
-            update_without_dirty(changed | self.class.serialized_attributes.keys)
+            update_without_dirty(changed | (attributes.keys & self.class.serialized_attributes.keys))
           else
             update_without_dirty
           end
diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index 1441421a80..74571d923a 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -298,6 +298,16 @@ class DirtyTest < ActiveRecord::TestCase
     end
   end
 
+  def test_save_should_not_save_serialized_attribute_with_partial_updates_if_not_present
+    with_partial_updates(Topic) do
+      Topic.create!(:author_name => 'Bill', :content => {:a => "a"})
+      topic = Topic.first(:select => 'id, author_name')
+      topic.update_attribute :author_name, 'John'
+      topic = Topic.first
+      assert_not_nil topic.content
+    end
+  end
+
   private
     def with_partial_updates(klass, on = true)
       old = klass.partial_updates?