SELECT * FROM innodb_trx; SELECT * FROM innodb_lock_waits; SELECT * FROM innodb_locks;

MySQL 5.5 -- innodb_lock_wait 锁 等待 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 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

root : 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)

root : 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)

root : 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; ###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 ；

root : 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)

由于没有产生锁等待，下面两个表没有数据 ；

root : information_schema 13:38:31> select * from innodb_lock_waits G Empty set (0.00 sec) : 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 ;

: 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) : 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) : 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？ 大家自己动手吧。