Use self.ignored_columns += instead of =

This is to accomodate prepended modules.

1 files changed, 1 insertions, 1 deletions

diff --git a/doc/development/what_requires_downtime.md b/doc/development/what_requires_downtime.md
index b9d1b95a4d7..f4cee410066 100644
--- a/doc/development/what_requires_downtime.md
+++ b/doc/development/what_requires_downtime.md
@@ -50,7 +50,7 @@ places. This can be done by defining the columns to ignore. For example, to igno
 
 ```ruby
 class User < ApplicationRecord
-  self.ignored_columns = %i[updated_at]
+  self.ignored_columns += %i[updated_at]
 end
 ```