Prevented belongs_to: touch propagating up if there are no changes being saved

activerecord/CHANGELOG.md

+*   Change belongs_to touch to be consistent with timestamp updates
+
+    If a model is set up with a belongs_to: touch relatinoship the parent
+    record will only be touched if the record was modified. This makes it
+    consistent with timestamp updating on the record itself.
+
+    *Brock Trappitt*
+
 *   Fixed the inferred table name of a HABTM auxiliar table inside a schema.
 
     Fixes #14824

activerecord/lib/active_record/associations/builder/belongs_to.rb

@@ -103,7 +103,7 @@ def self.add_touch_callbacks(model, reflection)
         BelongsTo.touch_record(record, foreign_key, n, touch)
       }
 
-      model.after_save    callback
+      model.after_save    callback, if: :changed?
       model.after_touch   callback
       model.after_destroy callback
     end

activerecord/test/cases/associations/belongs_to_associations_test.rb

@@ -369,6 +369,13 @@ def test_belongs_to_with_touch_option_on_update
     assert_queries(2) { line_item.update amount: 10 }
   end
 
+  def test_belongs_to_with_touch_option_on_empty_update
+    line_item = LineItem.create!
+    Invoice.create!(line_items: [line_item])
+
+    assert_queries(0) { line_item.save }
+  end
+
   def test_belongs_to_with_touch_option_on_destroy
     line_item = LineItem.create!
     Invoice.create!(line_items: [line_item])