フリー問題

問題文

An advertising team groups a click log by campaign and counts the rows. The plan shows an exchange between two stages, and the network graph shows traffic between all the workers. Why is the exchange unavoidable here?

選択肢

1. The operation needs a shuffle because the rows must be redistributed globally before the next step.
2. The operation needs a shuffle because the rows must be counted separately before the next step.
3. The operation needs a shuffle because the rows must be copied downward before the next step.
4. The operation needs a shuffle because the rows must be cached locally before the next step.