code: func (m *Meta) GetHistoryDDLJob(id int64) (*model.Job, error) {
  	startTime := time.Now()
  	job, err := m.getHistoryDDLJob(mDDLJobHistoryKey, id)
  	metrics.MetaHistogram.WithLabelValues(metrics.GetHistoryDDLJob, metrics.RetLabel(err)).Observe(time.Since(startTime).Seconds())
  	return job, errors.Trace(err)
  }
docs: // GetHistoryDDLJob gets a history DDL job.