Remove unnecessary will_change! calls causing excessive UPDATE queries

What went wrong:
- will_change! was called even when the value didn't actually change
- Example: user.mother_id = mother.id (assigning the same value)
- ActiveRecord marked all serialized columns as dirty
- Result: massive number of unnecessary UPDATE queries, causing outage

Root cause analysis:
- ActiveRecord's serialize columns automatically perform dirty tracking
  when hash values are modified internally
- Manual will_change! calls were completely unnecessary

Author: buzz-watcha

lib/coaster/serialized_properties.rb

@@ -27,7 +27,6 @@ def _write_sprop_value(key, value, apply_setter: true)
             setting = self.class.serialized_property_setting(key)
             return unless setting
             col = setting[:column]
-            send("#{col}_will_change!")
             hsh = send(col)
             if value.nil?
               hsh.delete(key.to_s)
@@ -312,7 +311,6 @@ def _define_serialized_property(serialize_column, key, getter: nil, setter: nil,
       if is_active_record
         define_method "#{key}_without_callback=".to_sym do |val|
           col = serialize_column
-          send("#{col}_will_change!")
           hsh = send(col)
           if val.nil?
             hsh.delete(key.to_s)

lib/coaster/version.rb

@@ -1,3 +1,3 @@
 module Coaster
-  VERSION = '1.4.38'
+  VERSION = '1.4.39'
 end

test/test_serialized_property_dirty.rb

@@ -0,0 +1,142 @@
+require 'test_helper'
+require 'minitest/autorun'
+
+module Coaster
+  class TestSerializedProperty < Minitest::Test
+    def setup
+    end
+
+    def teardown
+    end
+
+    def test_dirty
+      user = User.create(name: 'abc')
+      mother = User.create(name: 'mother')
+      user.mother = mother
+      assert_equal mother, user.mother
+      assert_equal mother.id, user.mother_id
+      assert_equal({"mother_id"=>mother.id}, user.data)
+      assert_equal({"data" => [{}, {"mother_id"=>mother.id}]}, user.changes)
+      assert_equal({"mother_id" => [nil, mother.id]}, user.sprop_changes)
+      assert_equal(true, user.mother_id_changed?)
+      assert_equal(nil, user.mother_id_was)
+      user.save!
+      user = User.find(user.id)
+      user.mother_id = mother.id
+      assert_equal(false, user.mother_id_changed?)
+      assert_equal({}, user.changes)
+      step_mother = User.create(name: 'step_mother')
+      user.mother = step_mother
+      assert_equal({"data" => [{"mother_id" => mother.id}, {"mother_id" => step_mother.id}]}, user.changes)
+      assert_equal({"mother_id" => [mother.id, step_mother.id]}, user.sprop_changes)
+    end
+
+    # Tests for dirty tracking optimization (skip dirty marking when value unchanged)
+    def test_same_value_setter_does_not_mark_dirty
+      user = User.create(name: 'test_same_value')
+      user.simple = 'initial_value'
+      user.save!
+
+      # Reload to clear dirty state
+      user.reload
+      assert_equal false, user.changed?
+
+      # Set same value - should NOT mark dirty
+      user.simple = 'initial_value'
+      assert_equal false, user.simple_changed?, 'Setting same value should not mark property as changed'
+      assert_equal false, user.changed?, 'Setting same value should not mark record as changed'
+    end
+
+    def test_different_value_setter_marks_dirty
+      user = User.create(name: 'test_different_value')
+      user.simple = 'initial_value'
+      user.save!
+      user.reload
+
+      # Set different value - should mark dirty
+      user.simple = 'new_value'
+      assert_equal true, user.simple_changed?, 'Setting different value should mark property as changed'
+      assert_equal true, user.changed?, 'Setting different value should mark record as changed'
+      assert_equal ['initial_value', 'new_value'], user.simple_change
+    end
+
+    def test_nil_to_value_marks_dirty
+      user = User.create(name: 'test_nil_to_value')
+      user.save!
+      user.reload
+
+      assert_nil user.simple
+      user.simple = 'some_value'
+      assert_equal true, user.simple_changed?
+      assert_equal [nil, 'some_value'], user.simple_change
+    end
+
+    def test_value_to_nil_marks_dirty
+      user = User.create(name: 'test_value_to_nil')
+      user.simple = 'some_value'
+      user.save!
+      user.reload
+
+      user.simple = nil
+      assert_equal true, user.simple_changed?
+      assert_equal ['some_value', nil], user.simple_change
+    end
+
+    def test_nil_to_nil_does_not_mark_dirty
+      user = User.create(name: 'test_nil_to_nil')
+      user.save!
+      user.reload
+
+      assert_nil user.simple
+      user.simple = nil
+      assert_equal false, user.simple_changed?, 'Setting nil to nil should not mark as changed'
+      assert_equal false, user.changed?
+    end
+
+    def test_same_value_via_write_attribute_does_not_mark_dirty
+      user = User.create(name: 'test_write_attr_same')
+      user.write_attribute(:simple, 'initial')
+      user.save!
+      user.reload
+
+      user.write_attribute(:simple, 'initial')
+      assert_equal false, user.simple_changed?
+      assert_equal false, user.changed?
+    end
+
+    def test_same_value_via_bracket_accessor_does_not_mark_dirty
+      user = User.create(name: 'test_bracket_same')
+      user[:simple] = 'initial'
+      user.save!
+      user.reload
+
+      user[:simple] = 'initial'
+      assert_equal false, user.simple_changed?
+      assert_equal false, user.changed?
+    end
+
+    def test_same_value_with_setter_proc_does_not_mark_dirty
+      student = Student.create(name: 'test_setter_same')
+      student.uppercase_name = 'hello'  # Stored as 'HELLO'
+      student.save!
+      student.reload
+
+      # Setting same raw input - setter transforms to same value
+      student.uppercase_name = 'hello'
+      assert_equal false, student.uppercase_name_changed?, 'Same value after setter transform should not mark dirty'
+      assert_equal false, student.changed?
+    end
+
+    def test_different_case_with_setter_proc_marks_dirty
+      student = Student.create(name: 'test_setter_diff')
+      student.uppercase_name = 'hello'  # Stored as 'HELLO'
+      student.save!
+      student.reload
+
+      # Setting different value
+      student.uppercase_name = 'world'  # Stored as 'WORLD'
+      assert_equal true, student.uppercase_name_changed?
+      assert_equal ['HELLO', 'WORLD'], student.uppercase_name_change
+    end
+  end
+end