atomic.rb

module ActiveRecord
  class Base
    def atomic &block
      self.class.transaction {
        lock!
        yield
      }
    end
  end
end

class Sequence < ActiveRecord::Base
  # so instead of this,
  def nextval
    Sequence.transaction {
      lock!
      returning self.value += 1 do
        save!
      end
    }
  end
  
  # we can do this
  def nextval
    atomic {
      returning self.value += 1 do
        save!
      end
    }
  end
end