：MySQL 5.5 — innodb_lock_wait
原文地址：http://www.mysqlops.com/2011/04/11/mysql-5-5-innodb_lock_wait.html
记得以前，当出现：ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction，要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
innodb_locks ## 当前出现的锁
innodb_lock_waits ## 锁等待的对应关系
看到这个就非常激动，这可是解决了一个大麻烦，先来看一下表结构：
[email protected] : information_schema 13:28:38> desc
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)
[email protected] : information_schema 13:28:56> desc 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)
[email protected] : information_schema 13:29:05> desc 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)
+————-+———————+——+—–+———+——-+
| 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)
[email protected] : information_schema 13:28:56> desc 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)
[email protected] : information_schema 13:29:05> desc 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)
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;
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;
update tx1 set c1 =’heyf’,c2 =’heyf’ where id = 3;
### 产生事务，在 innodb_trx 就有数据
root
@127.
0.0.
1 : information_schema
13:
38:
21
>
select
*
from 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)
*************************** 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
root
@127.
0.0.
1 : information_schema
13:
38:
31
>
select
*
from innodb_lock_waits \G
Empty set ( 0.00 sec)
root @127. 0.0. 1 : information_schema 13: 38: 57 > select * from innodb_locks \G
Empty set ( 0.00 sec)
Empty set ( 0.00 sec)
root @127. 0.0. 1 : information_schema 13: 38: 57 > select * from innodb_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 ;
update tx1 set c1 =’heyfffff’,c2 =’heyffffff’ where id = 3 ;
root @127. 0.0. 1 : information_schema 13: 39: 01 > select * from 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)
root @127. 0.0. 1 : information_schema 13: 40: 12 > select * from 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)
root @127. 0.0. 1 : information_schema 13: 40: 15 > select * from 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)
哈哈，有了以上这些信息，以下问题就迎刃而解啦。当前有哪些事务在等待锁？ 这些锁需要锁哪些表，锁哪些索引，锁哪些记录和值？处于等待状态的相关SQL是什么？在等待哪些事务完成 ？拥有当前锁的SQL是什么？
我想这些SQL对DBA来说不难吧？