MySQL事务未提交导致整个表锁死

2019/05/29 14:34
阅读数 575

问题及说明:

当一个SQL事务执行完了,但未COMMIT,后面的SQL想要执行就是被锁,超时结束;报错信息如下:

mysql> ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction

处理步骤:

该问题发生环境为MySQL 5.6,在MySQL 5.5版本后,information_schema 库中增加了三个关于锁的表,分别如下:

  • innodb_trx:当前运行的所有事务
  • innodb_locks:当前出现的锁
  • innodb_lock_waits:锁等待的对应关系 
    该问题可以直接从这个几张表入手,找到了一直没有提交的只读事务,然后 kill thread id
    ,最后确认只读事物是否被干掉了就OK了。解决步骤如下:
mysql> select * from information_schema.innodb_trx;
mysql> SHOW FULL PROCESSLIST;
mysql> kill 'thread id';
mysql> select * from information_schema.innodb_trx;

PS:如需要查看定位是哪条语句,可以在MySQL的binlog日志中查看根据id和时间定位查找语句。

MySQL事务知识点延伸:

1. 三个库的字段含义

mysql > desc information_schema.innodb_locks;
+-------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------------------+------+-----+---------+-------+
| lock_id | varchar(81) | NO | | | |#锁ID
| lock_trx_id | varchar(18) | NO | | | |#拥有锁的事务ID
| lock_mode | varchar(32) | NO | | | |#锁模式
| lock_type | varchar(32) | NO | | | |#锁类型
| lock_table | varchar(1024) | NO | | | |#被锁的表
| lock_index | varchar(1024) | YES | | NULL | |#被锁的索引
| lock_space | bigint(21) unsigned | YES | | NULL | |#被锁的表空间号
| lock_page | bigint(21) unsigned | YES | | NULL | |#被锁的页号
| lock_rec | bigint(21) unsigned | YES | | NULL | |#被锁的记录号
| lock_data | varchar(8192) | YES | | NULL | |#被锁的数据
+-------------+---------------------+------+-----+---------+-------+
10 rows in set (0.00 sec)

mysql> desc information_schema.innodb_lock_waits;
+-------------------+-------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------------+-------------+------+-----+---------+-------+
| requesting_trx_id | varchar(18) | NO | | | |#请求锁的事务ID
| requested_lock_id | varchar(81) | NO | | | |#请求锁的锁ID
| blocking_trx_id | varchar(18) | NO | | | |#当前拥有锁的事务ID
| blocking_lock_id | varchar(81) | NO | | | |#当前拥有锁的锁ID
+-------------------+-------------+------+-----+---------+-------+
4 rows in set (0.00 sec)

mysql> desc information_schema.innodb_trx;
+----------------------------+---------------------+------+-----+---------------------+-------+
| Field | Type | Null | Key | Default | Extra |
+----------------------------+---------------------+------+-----+---------------------+-------+
| trx_id | varchar(18) | NO | | | |#事务ID
| trx_state | varchar(13) | NO | | | |#事务状态:
| trx_started | datetime | NO | | 0000-00-00 00:00:00 | |#事务开始时间;
| trx_requested_lock_id | varchar(81) | YES | | NULL | |#innodb_locks.lock_id
| trx_wait_started | datetime | YES | | NULL | |#事务开始等待的时间
| trx_weight | bigint(21) unsigned | NO | | 0 | |#
| trx_mysql_thread_id | bigint(21) unsigned | NO | | 0 | |#事务线程ID
| trx_query | varchar(1024) | YES | | NULL | |#具体SQL语句
| trx_operation_state | varchar(64) | YES | | NULL | |#事务当前操作状态
| trx_tables_in_use | bigint(21) unsigned | NO | | 0 | |#事务中有多少个表被使用
| trx_tables_locked | bigint(21) unsigned | NO | | 0 | |#事务拥有多少个锁
| trx_lock_structs | bigint(21) unsigned | NO | | 0 | |#
| trx_lock_memory_bytes | bigint(21) unsigned | NO | | 0 | |#事务锁住的内存大小(B)
| trx_rows_locked | bigint(21) unsigned | NO | | 0 | |#事务锁住的行数
| trx_rows_modified | bigint(21) unsigned | NO | | 0 | |#事务更改的行数
| trx_concurrency_tickets | bigint(21) unsigned | NO | | 0 | |#事务并发票数
| trx_isolation_level | varchar(16) | NO | | | |#事务隔离级别
| trx_unique_checks | int(1) | NO | | 0 | |#是否唯一性检查
| trx_foreign_key_checks | int(1) | NO | | 0 | |#是否外键检查
| trx_last_foreign_key_error | varchar(256) | YES | | NULL | |#最后的外键错误
| trx_adaptive_hash_latched | int(1) | NO | | 0 | |#
| trx_adaptive_hash_timeout | bigint(21) unsigned | NO | | 0 | |#
+----------------------------+---------------------+------+-----+---------------------+-------+
22 rows in set (0.01 sec)

转自:
https://www.colabug.com/1912433.html

原文出处:https://www.cnblogs.com/leon0/p/10943711.html

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