While a flag stored in a table could be used for the same purpose, advisory locks are faster, avoid MVCC bloat, and are automatically cleaned up by the server at the end of the session.

• 虽然在一个表里面存储的一个标志也可以实现这个任务，劝告性锁速度更快，还避免了MVCC的膨胀，并且在服务器对应的会话结束的时候自动清理。