code: func (e *RecoverIndexExec) Next(ctx context.Context, req *chunk.RecordBatch) error {
  	req.Reset()
  	if e.done {
  		return nil
  	}
  
  	totalAddedCnt, totalScanCnt, err := e.backfillIndex(ctx)
  	if err != nil {
  		return err
  	}
  
  	req.AppendInt64(0, totalAddedCnt)
  	req.AppendInt64(1, totalScanCnt)
  	e.done = true
  	return nil
  }
docs: // Next implements the Executor Next interface.