1class MoveWatermarksFromCreationsToPhotos < ActiveRecord::Migration
2  def change
3    Photo.includes(:creation).find_each do |photo|
4      say("migrating watermark: #{photo.creation.watermark} to #{photo.id}")
5      photo.update_attribute(:watermark, photo.creation.watermark) if photo.creation.watermark.present?
6    end
7  end
8end