code: func (alloc *allocator) NextGlobalAutoID(tableID int64) (int64, error) {
  	var autoID int64
  	startTime := time.Now()
  	err := kv.RunInNewTxn(alloc.store, true, func(txn kv.Transaction) error {
  		var err1 error
  		m := meta.NewMeta(txn)
  		autoID, err1 = m.GetAutoTableID(alloc.dbID, tableID)
  		if err1 != nil {
  			return errors.Trace(err1)
  		}
  		return nil
  	})
  	metrics.AutoIDHistogram.WithLabelValues(metrics.GlobalAutoID, metrics.RetLabel(err)).Observe(time.Since(startTime).Seconds())
  	if alloc.isUnsigned {
  		return int64(uint64(autoID) + 1), err
  	}
  	return autoID + 1, err
  }
docs: // NextGlobalAutoID implements autoid.Allocator NextGlobalAutoID interface.