code: func (w *worker) waitDependencyJobFinished(job *model.Job, cnt *int) {
  	if job.DependencyID != noneDependencyJob {
  		intervalCnt := int(3 * time.Second / waitDependencyJobInterval)
  		if *cnt%intervalCnt == 0 {
  			logutil.Logger(w.logCtx).Info("[ddl] DDL job need to wait dependent job, sleeps a while, then retries it.",
  				zap.Int64("jobID", job.ID),
  				zap.Int64("dependentJobID", job.DependencyID),
  				zap.Duration("waitTime", waitDependencyJobInterval))
  		}
  		time.Sleep(waitDependencyJobInterval)
  		*cnt++
  	} else {
  		*cnt = 0
  	}
  }
docs: // waitDependencyJobFinished waits for the dependency-job to be finished.
  // If the dependency job isn't finished yet, we'd better wait a moment.