```ruby
class AddPostsOriginalUpdatedAt < ActiveRecord::Migration
  def change
    add_column :posts, :original_updated_at, :datetime
  end
end
```

Copy updated_at to original_updated_at for existing records
user
```ruby
class AddPostsOriginalUpdatedAt < ActiveRecord::Migration
  def change
    add_column :posts, :original_updated_at, :datetime

    execute 'UPDATE posts SET original_updated_at = updated_at'
  end
end
```
assistant