def UpdateCronJob(self,
                    cronjob_id,
                    last_run_status=db.Database.unchanged,
                    last_run_time=db.Database.unchanged,
                    current_run_id=db.Database.unchanged,
                    state=db.Database.unchanged,
                    forced_run_requested=db.Database.unchanged):
    """Updates run information for an existing cron job."""
    job = self.cronjobs.get(cronjob_id)
    if job is None:
      raise db.UnknownCronJobError("Cron job %s not known." % cronjob_id)

    if last_run_status != db.Database.unchanged:
      job.last_run_status = last_run_status
    if last_run_time != db.Database.unchanged:
      job.last_run_time = last_run_time
    if current_run_id != db.Database.unchanged:
      job.current_run_id = current_run_id
    if state != db.Database.unchanged:
      job.state = state
    if forced_run_requested != db.Database.unchanged:
      job.forced_run_requested = forced_run_requested