一、环境模拟
mysql> show create table t1;
+-------+-----------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+-----------------------------------------------------------------------------------------------------------------------+
| t1 | CREATE TABLE `t1` (
`id` int(11) NOT NULL,
`name` varchar(50) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
设置sql提交方式为手动commit，where条件没有索引
二、锁出现模拟
创建一下测试数据如下：
root@localhost : mirror:43: >select * from t1;
+------+--------+
| id | name |
+------+--------+
| 1 | mirror |
| 2 | mirror |
| 3 | mirror |
| 4 | mirror |
+------+--------+
4 rows in set (0.00 sec)
session 1：更新id为1的数据不提交
root@localhost : mirror:26: >update t1 set name='wang' where id=1;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1 Changed: 1 Warnings: 0
session 2：
root@localhost : mirror:45: >update t1 set name='zhang' where id=1;
session 3: 处理
1.查看是否有表被锁
root@localhost : (none):54: >show OPEN TABLES where In_use > 0;
+----------+-------+--------+-------------+
| Database | Table | In_use | Name_locked |
+----------+-------+--------+-------------+
| mirror | t1 | 1 | 0 |
+----------+-------+--------+-------------+
2.
show engine innodb status \G
LOCK WAIT 2 lock struct(s), heap size 1136, 13 row lock(s)
MySQL thread id 12, OS thread handle 140687159236352, query id 686 localhost root updating
update t1 set name='zhang' where id=1
------- TRX HAS BEEN WAITING 2 SEC FOR THIS LOCK TO BE GRANTED:
RECORD LOCKS space id 26 page no 3 n bits 72 index GEN_CLUST_INDEX of table `mirror`.`t1` trx id 1327 lock_mode X waiting
Record lock, heap no 2 PHYSICAL RECORD: n_fields 5; compact format; info bits 0
0: len 6; hex 000000000208; asc ;;
1: len 6; hex 000000000526; asc &;;
2: len 7; hex 3a0000002b03d1; asc : + ;;
3: len 4; hex 80000001; asc ;;
4: len 4; hex 77616e67; asc wang;;------------------
---TRANSACTION 1318, ACTIVE 2856 sec
3 lock struct(s), heap size 1136, 9 row lock(s), undo log entries 5
MySQL thread id 11, OS thread handle 140687158425344, query id 154 localhost root //也可以看到锁阻塞的sql 的id信息
Trx read view will not see trx with id >= 1318, sees < 1318
3.查看行锁的信息
root@localhost : (none):38: >select * from sys.innodb_lock_waits\G
*************************** 1. row ***************************
wait_started: 2021-11-18 14:37:53
wait_age: 00:00:46
wait_age_secs: 46 //锁等待时间，等待锁的事务
locked_table: `mirror`.`t1`
locked_index: GEN_CLUST_INDEX
locked_type: RECORD
waiting_trx_id: 1327
waiting_trx_started: 2021-11-18 14:27:48
waiting_trx_age: 00:10:51
waiting_trx_rows_locked: 8
waiting_trx_rows_modified: 0
waiting_pid: 12 //等待的线程
waiting_query: update t1 set name='zhang' where id=1
waiting_lock_id: 1327:26:3:2
waiting_lock_mode: X
blocking_trx_id: 1318
blocking_pid: 11
blocking_query: NULL
blocking_lock_id: 1318:26:3:2
blocking_lock_mode: X
blocking_trx_started: 2021-11-18 14:24:47
blocking_trx_age: 00:13:52
blocking_trx_rows_locked: 9
blocking_trx_rows_modified: 5
sql_kill_blocking_query: KILL QUERY 11 //阻塞的sql id
sql_kill_blocking_connection: KILL 11 杀掉锁的事务（杀掉阻塞上面语句的sql）
2 rows in set, 3 warnings (0.00 sec)
可以通过 KILL 11 直接杀掉阻塞的线程。
如果想知道哪条sql阻塞的，可以拿着sql_kill_blocking_connection的值11去threads查询
4、确认哪条sql阻塞的别的sql
root@localhost : (none):44: >select * from performance_schema.threads where processlist_id=11\G
*************************** 1. row ***************************
THREAD_ID: 36
NAME: thread/sql/one_connection
TYPE: FOREGROUND
PROCESSLIST_ID: 11
PROCESSLIST_USER: root //哪个用户发出的
PROCESSLIST_HOST: localhost //哪个客户端发出的
PROCESSLIST_DB: mirror //哪个数据库
PROCESSLIST_COMMAND: Sleep
PROCESSLIST_TIME: 1031
PROCESSLIST_STATE: NULL
PROCESSLIST_INFO: update t1 set name='wang' where id=1 //可以确认是这条sql阻塞了其他sql
PARENT_THREAD_ID: NULL
ROLE: NULL
INSTRUMENTED: YES
HISTORY: YES
CONNECTION_TYPE: Socket
THREAD_OS_ID: 22349
1 row in set (0.00 sec)
ps：select * from performance_schema.metadata_locks;
该条语句查看元数据锁，比如ddl锁