cache_key consults updated_on timestamp if present

- Extract max timestamp retrieval for cache_key
- Update changelog for cache_key changes

2 files changed, 22 insertions, 2 deletions

diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index af1845c937..5d558d5093 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1441,12 +1441,30 @@ class BasicsTest < ActiveRecord::TestCase
     assert_not_equal key, car.cache_key
   end
 
-  def test_cache_key_format_for_existing_record_with_nil_updated_at
+  def test_cache_key_format_for_existing_record_with_nil_updated_timestamps
     dev = Developer.first
-    dev.update_columns(updated_at: nil)
+    dev.update_columns(updated_at: nil, updated_on: nil)
     assert_match(/\/#{dev.id}$/, dev.cache_key)
   end
 
+  def test_cache_key_for_updated_on
+    dev = Developer.first
+    dev.updated_at = nil
+    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:nsec)}", dev.cache_key
+  end
+
+  def test_cache_key_for_newer_updated_at
+    dev = Developer.first
+    dev.updated_at += 3600
+    assert_equal "developers/#{dev.id}-#{dev.updated_at.utc.to_s(:nsec)}", dev.cache_key
+  end
+
+  def test_cache_key_for_newer_updated_on
+    dev = Developer.first
+    dev.updated_on += 3600
+    assert_equal "developers/#{dev.id}-#{dev.updated_on.utc.to_s(:nsec)}", dev.cache_key
+  end
+
   def test_touch_should_raise_error_on_a_new_object
     company = Company.new(:rating => 1, :name => "37signals", :firm_name => "37signals")
     assert_raises(ActiveRecord::ActiveRecordError) do
diff --git a/activerecord/test/schema/schema.rb b/activerecord/test/schema/schema.rb
index d789b6cb7a..a323b1e722 100644
--- a/activerecord/test/schema/schema.rb
+++ b/activerecord/test/schema/schema.rb
@@ -219,6 +219,8 @@ ActiveRecord::Schema.define do
     t.integer  :salary, :default => 70000
     t.datetime :created_at
     t.datetime :updated_at
+    t.datetime :created_on
+    t.datetime :updated_on
   end
 
   create_table :developers_projects, :force => true, :id => false do |t|