系统表介绍
rwlock_instances 表列举了服务器运行时，捕获的读写锁实例
| 列名 | 含义 |
|---|---|
| NAME | 锁监测器名称 |
| OBJECT_INSTANCE_BEGIN | 锁检测器内存地址 |
| WRITE_LOCKED_BY_THREAD_ID | 如有线程持有排它锁，此处为持有该锁的线程（thread）ID，其余时刻为空 |
| READ_LOCKED_BY_COUNT | 当一个线程支持有共享模式的 |
实例
+-------------------------------------------------------+-----------------------+---------------------------+----------------------+
| NAME | OBJECT_INSTANCE_BEGIN | WRITE_LOCKED_BY_THREAD_ID | READ_LOCKED_BY_COUNT |
+-------------------------------------------------------+-----------------------+---------------------------+----------------------+
| wait/synch/rwlock/session/LOCK_srv_session_collection | 33983192 | NULL | 0 |
| wait/synch/rwlock/sql/LOGGER::LOCK_logger | 34036096 | NULL | 0 |
| wait/synch/rwlock/sql/LOCK_system_variables_hash | 33969280 | NULL | 0 |
| wait/synch/rwlock/sql/LOCK_sys_init_connect | 33969408 | NULL | 0 |
| wait/synch/rwlock/sql/LOCK_sys_init_slave | 33969344 | NULL | 0 |
| wait/synch/rwlock/mysys/SAFE_HASH::lock | 34215520 | NULL | 0 |
| wait/synch/rwlock/sql/LOCK_dboptions | 34040992 | NULL | 0 |
| wait/synch/rwlock/sql/MDL_lock::rwlock | 36932952 | NULL | 0 |
| wait/synch/rwlock/sql/MDL_lock::rwlock | 36933560 | NULL | 0 |
| wait/synch/rwlock/sql/Trans_delegate::lock | 34038080 | NULL | 0 |
+-------------------------------------------------------+-----------------------+---------------------------+----------------------+
10 rows in set (0.00 sec)