今天测试test库的t表，发现delete from t;产生锁等等，于是乎就想办法查到是那个session造成的，不过很难找到，最终通过预估进行kill上锁的session，操作如下：
show engine innodb status\G
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TRANSACTIONS ------------ Trx id counter 387160 Purge done for trx‘s n:o < 387160 undo n:o < 0 state: running but idle History list length 1004 LIST OF TRANSACTIONS FOR EACH SESSION: ---TRANSACTION 0, not started MySQL thread id 9060, OS thread handle 0x7f29504ee700, query id 4240509 localhost root init show engine innodb status ---TRANSACTION 307468, not started MySQL thread id 5294, OS thread handle 0x7f2938825700, query id 3384276 localhost root cleaning up ---TRANSACTION 307463, ACTIVE 72199 sec 4 lock struct(s), heap size 1184, 11 row lock(s), undo log entries 4 MySQL thread id 4256, OS thread handle 0x7f29388a7700, query id 3384251 localhost root cleaning up TABLE LOCK table `test`.`t` trx id 307463 lock mode IX RECORD LOCKS space id 122 page no 3 n bits 80 index `PRIMARY` of table `test`.`t` trx id 307463 lock_mode X RECORD LOCKS space id 122 page no 4 n bits 80 index `idx_name` of table `test`.`t` trx id 307463 lock_mode X RECORD LOCKS space id 122 page no 4 n bits 80 index `idx_name` of table `test`.`t` trx id 307463 lock_mode X locks gap before rec |
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mysql> show processlist; +------+------+---------------------+------+-------------+-------+-----------------------------------------------------------------------+------------------+-----------+---------------+ | Id | User | Host | db | Command | Time | State | Info | Rows_sent | Rows_examined | +------+------+---------------------+------+-------------+-------+-----------------------------------------------------------------------+------------------+-----------+---------------+ | 4256 | root | localhost | test | Sleep | 72573 | | NULL | 7 | 7 | | 4375 | repl | 172.16.52.131:49285 | NULL | Binlog Dump | 75947 | Master has sent all binlog to slave; waiting for binlog to be updated | NULL | 0 | 0 | | 5294 | root | localhost | test | Sleep | 72553 | | NULL | 0 | 0 | | 9060 | root | localhost | test | Query | 0 | init | show processlist | 0 | 0 | | 9289 | root | localhost | NULL | Sleep | 40 | | NULL | 0 | 0 | +------+------+---------------------+------+-------------+-------+-----------------------------------------------------------------------+------------------+-----------+---------------+ 5 rows in set (0.00 sec) |
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mysql> select * from t; +----+----------+------+ | i | name | age | +----+----------+------+ | 1 | zhangsna | 20 | | 2 | zhangsna | 20 | | 3 | c | 23 | | 4 | c | 23 | | 5 | e | NULL | | 6 | f | NULL | | 19 | xiaoming | 23 | +----+----------+------+ 7 rows in set (0.00 sec) |
判断：
- 通过innodb status发现对t表上了表锁：TABLE LOCK table `test`.`t` trx id 307463 lock mode IX
- 通过select * from t发现该表有7行：7 rows in set (0.00 sec)
- 通过show processlist发现有一个会话的Rows_sent | Rows_examined为7 7 ，ID为4526
通过判断kill掉id为4526会话：
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mysql> kill 4256; Query OK, 0 rows affected (0.00 sec) |
在执行delete操作，顺利执行：
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mysql> delete from t; Query OK, 7 rows affected (0.01 sec) |