Don't calculate all in-place changes to determine if attribute_changed?

Calling `changed_attributes` will ultimately check if every mutable
attribute has changed in place. Since this gets called whenever an
attribute is assigned, it's extremely slow. Instead, we can avoid this
calculation until we actually need it.

Fixes #18029

1 files changed, 15 insertions, 0 deletions

diff --git a/activerecord/test/cases/dirty_test.rb b/activerecord/test/cases/dirty_test.rb
index eb9b1a2d74..1eaff5e293 100644
--- a/activerecord/test/cases/dirty_test.rb
+++ b/activerecord/test/cases/dirty_test.rb
@@ -698,6 +698,21 @@ class DirtyTest < ActiveRecord::TestCase
     assert binary.changed?
   end
 
+  test "attribute_changed? doesn't compute in-place changes for unrelated attributes" do
+    test_type_class = Class.new(ActiveRecord::Type::Value) do
+      define_method(:changed_in_place?) do |*|
+        raise
+      end
+    end
+    klass = Class.new(ActiveRecord::Base) do
+      self.table_name = 'people'
+      attribute :foo, test_type_class.new
+    end
+
+    model = klass.new(first_name: "Jim")
+    assert model.first_name_changed?
+  end
+
   private
     def with_partial_writes(klass, on = true)
       old = klass.partial_writes?