Future-proof Ruby on Rails migrations

double_user_balance_migration.rb

class DoubleUserBalance < ActiveRecord::Migration
  def up
    # Double user's balance
    prepared = ActiveRecord::Base.connection.raw_connection.prepare("
      UPDATE users
      SET balance = balance * ?
    ")
    prepared.execute(2)
    prepared.close
  end

  def down
    # Halve user's balance
    prepared = ActiveRecord::Base.connection.raw_connection.prepare("
      UPDATE users
      SET balance = balance * ?
    ")
    prepared.execute(1/2)
    prepared.close
  end
end