mysql事务未提交导致锁等待如何解决
1、实验环境
Myql版本5.7.17-log
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实验表结构
(root@localhost)[apex]> show create table test; +-------+-----------------------------------------------------------------------------------------------------------------------------------+ | Table| Create Table | +-------+-----------------------------------------------------------------------------------------------------------------------------------+ |test | CREATE TABLE `test` ( `x` int(11) NOT NULL, `y` int(11) DEFAULT NULL, PRIMARY KEY (`x`) )ENGINE=InnoDB DEFAULT CHARSET=gbk | +-------+-----------------------------------------------------------------------------------------------------------------------------------+ 1 row inset (0.01 sec)
插入数据
(root@localhost)[apex]> insert into test values(1,1); (root@localhost)[apex]> insert into test values(2,2); (root@localhost)[apex]> insert into test values(3,3);
2、锁产生步骤
会话一：开启事务，更新数据，不提交
(root@localhost)[apex]> begin; QueryOK, 0 rows affected (0.00 sec) (root@localhost)[apex]> update test set y=y+1 where x=1; QueryOK, 1 row affected (0.00 sec) Rowsmatched: 1 Changed: 1 Warnings: 0
查看当前连接id号（线程id号）
(root@localhost)[apex]> select connection_id(); +-----------------+ |connection_id() | +-----------------+ | 4 | +-----------------+ 1 row inset (0.00 sec)
会话二：开启另一个事务，更新同一行数据，
(root@localhost)[apex]> begin; QueryOK, 0 rows affected (0.00 sec) (root@localhost)[apex]> update test set y=y+1 where x=1; ERROR1205 (HY000): Lock wait timeout exceeded; try restarting transaction
执行update test set操作时，会卡在那边，不执行，经过50秒后，会报错；
（上面的卡住现象，是由于锁，可以通过查看表information_schema.innodb_lock，获取锁的状态）
(root@localhost)[information_schema]> select * from information_schema.innodb_locks; +-----------------+-------------+-----------+-----------+---------------+------------+------------+-----------+----------+-----------+ |lock_id | lock_trx_id | lock_mode| lock_type | lock_table | lock_index| lock_space | lock_page | lock_rec | lock_data | +-----------------+-------------+-----------+-----------+---------------+------------+------------+-----------+----------+-----------+ |757082:3279:3:2 | 757082 | X | RECORD | `apex`.`test` | PRIMARY | 3279 | 3 | 2 | 1 | |757081:3279:3:2 | 757081 | X | RECORD | `apex`.`test` | PRIMARY | 3279 | 3 | 2 | 1 | +-----------------+-------------+-----------+-----------+---------------+------------+------------+-----------+----------+-----------+ 2 rowsin set, 1 warning (0.00 sec)
查看当前连接id号（线程id号）
(root@localhost) [apex]> selectconnection_id(); +-----------------+ |connection_id() | +-----------------+ | 5 | +-----------------+ 1 row inset (0.00 sec)
以上说的50秒，是系统参数innodb_lock_wait_timeout决定的
(root@localhost)[apex]> show variables like 'innodb_lock_wait_timeout'; +--------------------------+-------+ |Variable_name | Value | +--------------------------+-------+ | innodb_lock_wait_timeout| 50 | +--------------------------+-------+ 1 row inset (0.00 sec)
3、MySQL如何查看未提交的事务
方法一：
(root@localhost)[performance_schema]> SELECT * FROMinformation_schema.INNODB_TRX\G ***************************1. row *************************** trx_id: 756996 trx_state: RUNNING trx_started: 2017-05-08 15:08:07 trx_requested_lock_id: NULL trx_wait_started: NULL trx_weight: 3 trx_mysql_thread_id: 4 trx_query: NULL trx_operation_state: NULL trx_tables_in_use: 0 trx_tables_locked: 1 trx_lock_structs: 2 trx_lock_memory_bytes: 1136 trx_rows_locked: 1 trx_rows_modified: 1 trx_concurrency_tickets: 0 trx_isolation_level: REPEATABLE READ trx_unique_checks: 1 trx_foreign_key_checks: 1 trx_last_foreign_key_error:NULL trx_adaptive_hash_latched: 0 trx_adaptive_hash_timeout: 0 trx_is_read_only: 0 trx_autocommit_non_locking:0 1 row inset (0.00 sec)
通过以上可看出线程id为4 一直未提交，事务开始的时间为2017-05-08 15:08:07。
方法二：通过 show engine innodb status\G
其中有一段关于事务的描述
TRANSACTIONS ------------ Trx idcounter 756998 Purgedone for trx's n:o < 0 undo n:o < 0 state: running but idle Historylist length 0 LIST OFTRANSACTIONS FOR EACH SESSION: ---TRANSACTION421519065333360, not started 0 lockstruct(s), heap size 1136, 0 row lock(s) ---TRANSACTION421519065332448, not started 0 lockstruct(s), heap size 1136, 0 row lock(s) ---TRANSACTION756996, ACTIVE 914 sec 2 lockstruct(s), heap size 1136, 1 row lock(s), undo log entries 1 MySQL thread id 4, OS thread handle 140041791522560, query id25 localhost root
从以上也可以看出线程id号为4的事务一直未提交。
4、如何解决未提交的事务
方法一：如果能知道哪个用户在执行这个操作，让他提交一下（这种可能性很小）
方法二：kill掉这个线程id号，让事务回滚，
(root@localhost)[information_schema]> show processlist; +----+-----------------+------------------+--------------------+---------+------+------------------------+------------------+ | Id |User | Host | db | Command | Time | State | Info | +----+-----------------+------------------+--------------------+---------+------+------------------------+------------------+ | 1 | event_scheduler | localhost | NULL | Daemon | 4469 | Waiting on empty queue | NULL | | 4 | root | localhost | apex | Sleep | 871| | NULL | | 5 | root | localhost | apex | Sleep | 82| | NULL | | 6 | root | localhost | information_schema | Query | 0| starting | showprocesslist | | 7 | root | 192.168.1.1:3708 | NULL | Sleep | 3221 | | NULL | +----+-----------------+------------------+--------------------+---------+------+------------------------+------------------+ 5 rowsin set (0.00 sec) (root@localhost)[information_schema]> kill 4; QueryOK, 0 rows affected (0.01 sec)
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