From 8f9a7ca854ffda26c5ce9aed2aec10bf155d0463 Mon Sep 17 00:00:00 2001
From: Valery Sizov <valery@gitlab.com>
Date: Mon, 1 Aug 2016 18:34:17 +0300
Subject: Revert the revert of Optimistic Locking

---
 config/initializers/ar_monkey_patch.rb | 57 ++++++++++++++++++++++++++++++++++
 1 file changed, 57 insertions(+)
 create mode 100644 config/initializers/ar_monkey_patch.rb

(limited to 'config/initializers')

diff --git a/config/initializers/ar_monkey_patch.rb b/config/initializers/ar_monkey_patch.rb
new file mode 100644
index 00000000000..0da584626ee
--- /dev/null
+++ b/config/initializers/ar_monkey_patch.rb
@@ -0,0 +1,57 @@
+# rubocop:disable Lint/RescueException
+
+# This patch fixes https://github.com/rails/rails/issues/26024
+# TODO: Remove it when it's no longer necessary
+
+module ActiveRecord
+  module Locking
+    module Optimistic
+      # We overwrite this method because we don't want to have default value
+      # for newly created records
+      def _create_record(attribute_names = self.attribute_names, *) # :nodoc:
+        super
+      end
+
+      def _update_record(attribute_names = self.attribute_names) #:nodoc:
+        return super unless locking_enabled?
+        return 0 if attribute_names.empty?
+
+        lock_col = self.class.locking_column
+
+        previous_lock_value = send(lock_col).to_i
+
+        # This line is added as a patch
+        previous_lock_value = nil if previous_lock_value == '0' || previous_lock_value == 0
+
+        increment_lock
+
+        attribute_names += [lock_col]
+        attribute_names.uniq!
+
+        begin
+          relation = self.class.unscoped
+
+          affected_rows = relation.where(
+            self.class.primary_key => id,
+            lock_col => previous_lock_value,
+          ).update_all(
+            attributes_for_update(attribute_names).map do |name|
+              [name, _read_attribute(name)]
+            end.to_h
+          )
+
+          unless affected_rows == 1
+            raise ActiveRecord::StaleObjectError.new(self, "update")
+          end
+
+          affected_rows
+
+        # If something went wrong, revert the version.
+        rescue Exception
+          send(lock_col + '=', previous_lock_value)
+          raise
+        end
+      end
+    end
+  end
+end
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