From f08bc757ebe108df46d76d6fd0029546539f817f Mon Sep 17 00:00:00 2001
From: bogdanvlviv <bogdanvlviv@gmail.com>
Date: Sat, 29 Apr 2017 08:21:05 +0000
Subject: [PATCH] Fix destroy with locking_column value null

Fix destroying existing object does not work well when optimistic
locking enabled and `locking column` is null in the database.

Follow 22a822e5813ef7ea9ab6dbbb670a363899a083af, #28914
---
 activerecord/CHANGELOG.md                     |  5 ++++
 .../lib/active_record/locking/optimistic.rb   |  2 +-
 activerecord/test/cases/locking_test.rb       | 25 +++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index c65deffa8b..f361e44fcd 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,8 @@
+*   Fix destroying existing object does not work well when optimistic locking enabled and
+    `locking column` is null in the database.
+
+    *bogdanvlviv*
+
 *   Use bulk INSERT to insert fixtures for better performance.
 
     *Kir Shatrov*
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index f8fcb7ccaa..522da6a571 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -128,7 +128,7 @@ module ActiveRecord
 
           if locking_enabled?
             locking_column = self.class.locking_column
-            relation = relation.where(locking_column => _read_attribute(locking_column))
+            relation = relation.where(locking_column => read_attribute_before_type_cast(locking_column))
           end
 
           relation
diff --git a/activerecord/test/cases/locking_test.rb b/activerecord/test/cases/locking_test.rb
index 2b139a5da4..703487db35 100644
--- a/activerecord/test/cases/locking_test.rb
+++ b/activerecord/test/cases/locking_test.rb
@@ -453,6 +453,31 @@ class OptimisticLockingWithSchemaChangeTest < ActiveRecord::TestCase
     PersonalLegacyThing.reset_column_information
   end
 
+  def test_destroy_existing_object_with_locking_column_value_null_in_the_database
+    ActiveRecord::Base.connection.execute("INSERT INTO lock_without_defaults(title) VALUES('title1')")
+    t1 = LockWithoutDefault.last
+
+    assert_equal 0, t1.lock_version
+    assert_nil t1.lock_version_before_type_cast
+
+    t1.destroy
+
+    assert t1.destroyed?
+  end
+
+  def test_destroy_stale_object
+    t1 = LockWithoutDefault.create!(title: "title1")
+    stale_object = LockWithoutDefault.find(t1.id)
+
+    t1.update!(title: "title2")
+
+    assert_raises(ActiveRecord::StaleObjectError) do
+      stale_object.destroy!
+    end
+
+    refute stale_object.destroyed?
+  end
+
   private
 
     def add_counter_column_to(model, col = "test_count")