code: func (e *TableScanExec) nextHandle() (handle int64, found bool, err error) {
  	for {
  		handle, found, err = e.t.Seek(e.ctx, e.seekHandle)
  		if err != nil || !found {
  			return 0, false, err
  		}
  		return handle, true, nil
  	}
  }
docs: // nextHandle gets the unique handle for next row.