mysql8查看锁

一。准备环境

1.登录mysql，设置锁等待时间，然后退出。

mysql> set global innodb_lock_wait_timeout=1200;
Query OK, 0 rows affected (0.00 sec)
 

2.再次登录MySQL。打开第一个session

 3.登录msyql，打开第二个session

2.登录打开第二个session
mysql> set autocommit=0;
Query OK, 0 rows affected (0.00 sec)
 
mysql> 
mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
|            0 |
+--------------+
1 row in set (0.00 sec)
 
mysql> use test
 
mysql> update temp set name='bb' where id=1;  #执行这条sql，会一直卡住。

4.登录MySQL，打开第三个session。

a：查看

mysql> select trx_id,trx_state,trx_started,trx_tables_locked,trx_rows_locked,trx_query from information_schema.innodb_trx;

看上图trx_state的状态LOCK_WAIT，同时trx_query对应的sql语句，说明执行这条sql阻塞了。事务id的字段trx_id的值1755425

b：查看

mysql> select ENGINE_LOCK_ID,ENGINE_TRANSACTION_ID,LOCK_MODE,LOCK_TYPE,INDEX_NAME,OBJECT_SCHEMA,OBJECT_NAME,LOCK_DATA,LOCK_STATUS,THREAD_ID from performance_schema.data_locks;

看上图的lock_status出现了一个WAITING,同时THREAD_ID为57的线程处于等待状态。对应的ENGINE_TRANSACTION_ID的值就是a操作的图字段trx_id的值1755425。

4.还要查看锁事务的对应关系，

mysql> select locked_table_name,locked_index,waiting_pid,waiting_lock_id,blocking_lock_id,blocking_pid from sys.innodb_lock_waits;

再次对比下。可以找到关系，1等待的事务处理，是被2阻塞了。也就是锁住了，需要2释放锁，1才可以执行

mysql> select ENGINE_LOCK_ID,ENGINE_TRANSACTION_ID,LOCK_MODE,LOCK_TYPE,INDEX_NAME,OBJECT_SCHEMA,OBJECT_NAME,LOCK_DATA,LOCK_STATUS,THREAD_ID from performance_schema.data_locks;
 
mysql> select locked_table_name,locked_index,waiting_pid,waiting_lock_id,blocking_lock_id,blocking_pid from sys.innodb_lock_waits;

 同时，查看waiting_pid跟blocking_pid的值就是线程id，对应processlist

mysql> select locked_table_name,locked_index,waiting_pid,waiting_lock_id,blocking_lock_id,blocking_pid from sys.innodb_lock_waits;
 
mysql> show processlist;

5.现在上面图看不到blocking_pid对应的线程THREAD_PID

mysql>  select ENGINE_LOCK_ID,ENGINE_TRANSACTION_ID,LOCK_MODE,LOCK_TYPE,INDEX_NAME,OBJECT_SCHEMA,OBJECT_NAME,LOCK_DATA,LOCK_STATUS,THREAD_ID from performance_schema.data_locks;
 
mysql> select locked_table_name,locked_index,waiting_pid,waiting_lock_id,blocking_lock_id,blocking_pid from sys.innodb_lock_waits;

6.通过上图可以看到。 blocking_pid为15 对应的线程THREAD_PID 为56.

waiting_pid为16 对应的线程THREAD_PID 为57.

mysql> select THREAD_ID,EVENT_ID,EVENT_NAME,SQL_TEXT from performance_schema.events_statements_history where THREAD_ID in (56,57) order by THREAD_ID,EVENT_ID;

 从图上分析，就可以看出blocking_pid，也就是已经锁了执行的sql是啥。