フリー問題

問題文

Two sessions must both look at the same rows and be sure that nobody changes them, while still allowing each other to look. Which lock fits?

選択肢

1. Both sessions should choose the exclusive update lock on the rows they need concurrently.
2. Both sessions should choose the common read lock on the rows they need concurrently.
3. Both sessions should choose the intention gap lock on the rows they need concurrently.
4. Both sessions should choose the brief metadata lock on the rows they need concurrently.