查看Mysql正在执行的事务、锁、等待

对于异常：

ERROR 1205 (HY000): Lock wait timeoutexceeded; try restarting transaction
解决是一件麻烦的事情。
特别是当一个SQL执行完了，但未COMMIT，后面的SQL想要执行就是被锁，超时结束；
DBA光从数据库无法着手找出源头是哪个SQL锁住了；
有时候看看show engine innodb status; , 并结合 show full processlist;能暂时解决问题；但一直不能精确定位；
在5.5中，information_schema库中增加了三个关于锁的表（MEMORY引擎）；
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
注意：如果使用select * from table for update时，上面的参数无法看到锁的情况，只有在show engine innodb status能查到。
另外还可以查看参数：

mysql> show status like ‘innodb_row_lock_%’;
±------------------------------±----------+
| Variable_name | Value |
±------------------------------±----------+
| Innodb_row_lock_current_waits | 2 |
| Innodb_row_lock_time | 334377476 |
| Innodb_row_lock_time_avg | 50678 |
| Innodb_row_lock_time_max | 51974 |
| Innodb_row_lock_waits | 6598 |
±------------------------------±----------+

解释如下：
Innodb_row_lock_current_waits : 当前等待锁的数量
Innodb_row_lock_time : 系统启动到现在，锁定的总时间长度
Innodb_row_lock_time_avg : 每次平均锁定的时间
Innodb_row_lock_time_max : 最长一次锁定时间
Innodb_row_lock_waits : 系统启动到现在总共锁定的次数
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
±------------±--------------------±-----±----±--------±------+
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
±------------------±------------±-----±----±--------±------+
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 ||#
±---------------------------±--------------------±-----±----±--------------------±------+
下面我们来动手看看数据吧：
建立测试数据：

use test;
create table tx1
(id int primary key ,
c1 varchar(20),
c2 varchar(30))
engine=innodb default charset = utf8 ;
insert into tx1 values
(1,‘aaaa’,‘aaaaa2’),
(2,‘bbbb’,‘bbbbb2’),
(3,‘cccc’,‘ccccc2’);
commit;
产生事务：

Session1：
start transaction;
update tx1 set c1=‘heyf’,c2=‘heyf’ where id =3 ;
产生事务，在innodb_trx就有数据 ；
select * from information_schema.innodb_trx\G;
*************************** 1. row***************************
trx_id: 3669D82
trx_state: RUNNING
trx_started: 2010-12-24 13:38:06
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 3
trx_mysql_thread_id: 2344
trx_query: NULL
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 0
trx_lock_structs: 2
trx_lock_memory_bytes: 376
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: 10000
1 row in set (0.00 sec)
由于没有产生锁等待，下面两个表没有数据 ；
select * from information_schema.innodb_lock_waits\G;
Empty set (0.00 sec)
[email protected] :information_schema 13:38:57> select * frominnodb_locks G
Empty set (0.00 sec)
产生锁等待
session 2：
start transaction;
update tx1 set c1=‘heyfffff’,c2=‘heyffffff’ where id =3 ;
select * from information_schema.innodb_trx\G;
*************************** 1. row***************************
trx_id: 3669D83 ##第2个事务
trx_state: LOCK WAIT ## 处于等待状态
trx_started: 2010-12-24 13:40:07
trx_requested_lock_id: 3669D83:49:3:4 ##请求的锁ID
trx_wait_started: 2010-12-24 13:40:07
trx_weight: 2
trx_mysql_thread_id: 2346 ##线程 ID
trx_query: update tx1 set c1=‘heyfffff’,c2=‘heyffffff’ where id=3
trx_operation_state: starting index read
trx_tables_in_use: 1 ##需要用到1个表
trx_tables_locked: 1 ##有1个表被锁
trx_lock_structs: 2
trx_lock_memory_bytes: 376
trx_rows_locked: 1
trx_rows_modified: 0
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: 10000
*************************** 2. row***************************
trx_id: 3669D82 ##第1个事务
trx_state: RUNNING
trx_started: 2010-12-24 13:38:06
trx_requested_lock_id: NULL
trx_wait_started: NULL
trx_weight: 3
trx_mysql_thread_id: 2344
trx_query: NULL
trx_operation_state: NULL
trx_tables_in_use: 0
trx_tables_locked: 0
trx_lock_structs: 2
trx_lock_memory_bytes: 376
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: 10000
2 rows in set (0.00 sec)
select * from information_schema.innodb_locks\G;
*************************** 1. row***************************
lock_id: 3669D83:49:3:4 ## 第2个事务需要的锁
lock_trx_id: 3669D83
lock_mode: X
lock_type: RECORD
lock_table: test.tx1
lock_index: PRIMARY
lock_space: 49
lock_page: 3
lock_rec: 4
lock_data: 3
*************************** 2. row***************************
lock_id: 3669D82:49:3:4 ## 第1个事务需要的锁
lock_trx_id: 3669D82
lock_mode: X
lock_type: RECORD
lock_table: test.tx1
lock_index: PRIMARY
lock_space: 49
lock_page: 3
lock_rec: 4
lock_data: 3
2 rows in set (0.00 sec)
select * from information_schema.innodb_lock_waits\G;
*************************** 1. row***************************
requesting_trx_id: 3669D83 ## 请求锁的事务
requested_lock_id: 3669D83:49:3:4 ## 请求锁的锁ID
blocking_trx_id: 3669D82 ## 拥有锁的事务
blocking_lock_id: 3669D82:49:3:4 ## 拥有锁的锁ID
1 row in set (0.00 sec)