可选链运算符(?.),大家都很熟悉了,直接看个例子:
const result obj?.a?.b?.c?.d
很简单例子,上面代码?前面的属性如果是空值(null或undefined),则result值是undefined,反之…
#查询当前数据库全部线程show full processlist #查询当前运行的全部事务select * from information_schema.innodb_trx#查询锁情况select * from information_schema.innodb_locks#查询锁等待情况select * from information_schema.innodb_lock_waits #查看mysql设置等待锁时长…