codeocean/db/migrate/20140918063522_add_hashed_content_to_files.rb

class AddHashedContentToFiles < ActiveRecord::Migration
  def change
    add_column :files, :hashed_content, :string

    reversible do |direction|
      direction.up do
        CodeOcean::File.all.each(&:save)
      end
    end
  end
end