实战篇：如何查看mysql里面的锁

Posted 2022-03-29 进击的CJR

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通过查询表统计信息查看

information_schema库下相关事务表和锁相关信息表介绍

innodb_trx

存储了当前正在执行的事务信息

trx_id：事务ID。

trx_state：事务状态，有以下几种状态：RUNNING、LOCK WAIT、ROLLING BACK 和 COMMITTING。

trx_started：事务开始时间。

trx_requested_lock_id：事务当前正在等待锁的标识，可以和 INNODB_LOCKS 表 JOIN 以得到更多详细信息。

trx_wait_started：事务开始等待的时间。

trx_mysql_thread_id：事务线程 ID，可以和 PROCESSLIST 表 JOIN。

trx_tables_locked：表示该事务目前加了多少个表级锁。

trx_lock_structs：表示该事务生成了多少个内存中的锁结构。

trx_lock_memory_bytes：事务锁住的内存大小，单位为 BYTES。

trx_rows_locked：表示该事务目前加了多少个行级锁。

innodb_locks

记录了锁信息

如果一个事务想要获取到某个锁但未获取到，则记录该锁信息

如果一个事务获取到了某个锁，但是这个锁阻塞了别的事务，则记录该锁信息

但是无法通过该表查询到谁被阻塞，谁持有未释放。

lock_id：锁 ID。

lock_trx_id：拥有锁的事务 ID。可以和 INNODB_TRX 表 JOIN 得到事务的详细信息。

lock_mode：锁的模式。

lock_type：锁的类型。RECORD 代表行级锁，TABLE 代表表级锁。

lock_table：被锁定的或者包含锁定记录的表的名称。

innodb_lock_waits

表明每个阻塞的事务是因为获取不到哪个事务持有的锁而被阻塞

requesting_trx_id：--获取不到锁而被阻塞的事务id（等待方）

requested_lock_id：-- 请求锁ID ，事务所等待的锁定的 ID。可以和 INNODB_LOCKS 表 JOIN。

blocking_trx_id： --获取到别的事务需要的锁而阻塞其事务的事务id（当前持有方，待释放）

blocking_lock_id： --这一事务的锁的 ID，该事务阻塞了另一事务的运行。可以和 INNODB_LOCKS 表 JOIN。

processlist

id:标识ID。这与在SHOW PROCESSLIST语句的Id列、Performance Schema threads表的PROCESSLIST_ID列中显示的值类型相同，并由CONNECTION_ID()函数返回

user:发出该语句的mysql用户。

host：发出该语句的客户机的主机名(系统用户除外，没有主机)。

db：默认数据库。

command：线程正在执行的命令的类型。

time：线程处于当前状态的时间(以秒为单位)。

state：指示线程正在执行的操作、事件或状态。

info：线程正在执行的语句，如果没有执行任何语句，则为NULL。

如何借助这几张表来定位到有行锁等待

（1）查看当前有无锁等待

mysql> show status like innodb_row_lock%;

（2）查看哪个事务在等待(被阻塞了)

mysql> select * from information_schema.INNODB_TRX WHERE trx_state=LOCK WAIT\\G

trx_state 表示该事务处于锁等待状态。

trx_query : 当前被阻塞的操作是select * from actor where actor_id=1 for update。

从trx_mysql_thread_id和trx_id可以看到这里查到当前被阻塞的事务的：

线程ID是 971，注意说的是线程id

事务ID是3934

（3）查询该事务被哪个事务给阻塞了从innodb_trx获取到被阻塞的trx_id是3934，阻塞该事务的事务id是3933

mysql> SELECT * FROM performance_schema.threads WHERE processlist_id=970\\G

（4）根据trx_id，从innodb_trx表可查询到trx_mysql_thread_id线程id为970

mysql> select * from information_schema.innodb_trx where trx_id=3933 \\G

（5）根据线程id，查询表拿到thread_id为995

mysql> SELECT * FROM performance_schema.threads WHERE processlist_id=970\\G

（6）根据thread_id，查询当前锁源的sql

mysql> SELECT * FROM performance_schema.events_statements_current WHERE thread_id=995\\G

整个流程如下：

（1）首先查询是否有锁，根据锁查到被锁的trx_id

（2）根据被锁的trx_id可以查到锁源的trx_id

（3）根据锁源的trx_id查到trx_mysql_thread_id

（4）再根据trx_mysql_thread_id查到thread_id

（5）最后，用thread_id查找到锁源的sql

此外，第一步发现锁的方式，也可直接获取到锁源trx_id和被锁trx_id

但是这种方法在mysql8.0已经被移除，介绍另外一张表

sys.innodb_lock_waits 表

locked_table : 哪张表出现的等待

waiting_trx_id: 等待的事务(与上个视图trx_id 对应)

waiting_pid : 等待的线程号(与上个视图trx_mysql_thread_id)

blocking_trx_id : 锁源的事务ID

blocking_pid : 锁源的线程号

mysql> select * from sys.innodb_lock_waits\\G

获取到锁源的blocking_pid 976（=processlist表的id），根据此id找到thread_id，再根据thread_id找到对应的sql

总结：

两种找到锁源SQL步骤是一样的

锁源的事务trx_id -->pnformaction_schema.processlist表的线程id-->performance_schema.threads表的thread_id-->performance_schema.events_statements_current 或performance_schema.events_statements_history查看sql

注：下面所指的id含义相同

information_schema.innodb_trx(trx_mysql_thread_id)

information_schema.processlist(id)

sys.innodb_lock_waits(waiting_pid,blocking_pid)

sys.sys.innodb_lock_waits的应用

1）查看锁等待相关的（阻塞线程、被阻塞线程信息及相关用户、IP、PORT、locked_type锁类型）
SELECT locked_table,
       locked_index,
       locked_type,
       blocking_pid,
       concat(T2.USER,@,T2.HOST) AS "blocking(user@ip:port)",
       blocking_lock_mode,
       blocking_trx_rows_modified,
       waiting_pid,
       concat(T3.USER,@,T3.HOST) AS "waiting(user@ip:port)",
       waiting_lock_mode,
       waiting_trx_rows_modified,
       wait_age_secs,
       waiting_query
FROM sys.x$innodb_lock_waits T1
LEFT JOIN INFORMATION_SCHEMA.processlist T2 ON T1.blocking_pid=T2.ID
LEFT JOIN INFORMATION_SCHEMA.processlist T3 ON T3.ID=T1.waiting_pid;

2）等待的持续时间（单位秒>20s） 
  SELECT trx_mysql_thread_id AS PROCESSLIST_ID,
       NOW(),
       TRX_STARTED,
       TO_SECONDS(now())-TO_SECONDS(trx_started) AS TRX_LAST_TIME ,
       USER,
       HOST,
       DB,
       TRX_QUERY
FROM INFORMATION_SCHEMA.INNODB_TRX trx
JOIN sys.innodb_lock_waits lw ON trx.trx_mysql_thread_id=lw.waiting_pid
JOIN INFORMATION_SCHEMA.processlist pcl ON trx.trx_mysql_thread_id=pcl.id
WHERE trx_mysql_thread_id != connection_id()
  AND TO_SECONDS(now())-TO_SECONDS(trx_started) >= 20 ;

show engine innodb status

将锁信息打印出来

mysql> set global innodb_status_output_locks =ON;

执行如下sql，fisrt_name上有普通二级索引

begin; <br/>

select * from actor where first_name >A and first_name <B for update; <br/>查询得到该事务ID，方面后面观察验证 <br/>

show engine innodb status看到的事务信息如下

我将注释写在#后面

------------
TRANSACTIONS
------------
Trx id counter 3957                                                          #下一个待分配的事务id
Purge done for trxs n:o < 3930 undo n:o < 0 state: running but idle
History list length 0
LIST OF TRANSACTIONS FOR EACH SESSION:                                       #各个事务信息
---TRANSACTION 421799341399664, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421799341400576, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421799341403312, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 421799341398752, not started
0 lock struct(s), heap size 1136, 0 row lock(s)
---TRANSACTION 3956, ACTIVE 25 sec                                           #事务id为3956的事务，活跃时间25秒
3 lock struct(s), heap size 1136, 27 row lock(s)
MySQL thread id 991, OS thread handle 140323910289152, query id 10636 localhost root
TABLE LOCK table `sakila`.`actor` trx id 3956 lock mode IX                  #事务id为3956的事务，对`sakila`.`actor`加了表级别意向独占锁 IX
RECORD LOCKS space id 45 page no 5 n bits 272 index idx_actor_first of table `sakila`.`actor` trx id 3956 lock_mode X
Record lock, heap no 2 PHYSICAL RECORD: n_fields 2; compact format; info bits 0    #idx_actor_first 是二级索引，lock_mode X Record lock 表示X型的next_key 锁
 0: len 4; hex 4144414d; asc ADAM;;
 1: len 2; hex 0047; asc  G;;

Record lock, heap no 3 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 4144414d; asc ADAM;;
 1: len 2; hex 0084; asc   ;;

Record lock, heap no 4 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 2; hex 414c; asc AL;;
 1: len 2; hex 00a5; asc   ;;

Record lock, heap no 5 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 414c414e; asc ALAN;;
 1: len 2; hex 00ad; asc   ;;

Record lock, heap no 6 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 414c42455254; asc ALBERT;;
 1: len 2; hex 007d; asc  ;;

Record lock, heap no 7 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 414c42455254; asc ALBERT;;
 1: len 2; hex 0092; asc   ;;

Record lock, heap no 8 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 414c4543; asc ALEC;;
 1: len 2; hex 001d; asc   ;;

Record lock, heap no 9 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 414e47454c41; asc ANGELA;;
 1: len 2; hex 0041; asc  A;;

Record lock, heap no 10 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 414e47454c41; asc ANGELA;;
 1: len 2; hex 0090; asc   ;;

Record lock, heap no 11 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 8; hex 414e47454c494e41; asc ANGELINA;;
 1: len 2; hex 004c; asc  L;;

Record lock, heap no 12 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 414e4e45; asc ANNE;;
 1: len 2; hex 0031; asc  1;;

Record lock, heap no 13 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 415544524559; asc AUDREY;;
 1: len 2; hex 0022; asc  ";;

Record lock, heap no 14 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 6; hex 415544524559; asc AUDREY;;
 1: len 2; hex 00be; asc   ;;

Record lock, heap no 15 PHYSICAL RECORD: n_fields 2; compact format; info bits 0
 0: len 4; hex 42454c41; asc BELA;;
 1: len 2; hex 00c4; asc   ;;

RECORD LOCKS space id 45 page no 3 n bits 272 index PRIMARY of table `sakila`.`actor` trx id 3956 lock_mode X locks rec but not gap
Record lock, heap no 30 PHYSICAL RECORD: n_fields 6; compact format; info bits 0       # trx id 3956 聚簇索引PRIMARY ，lock_mode X locks rec but not gap Record lock 表示X型记录锁
 0: len 2; hex 001d; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b0228; asc     + (;;
 3: len 4; hex 414c4543; asc ALEC;;
 4: len 5; hex 5741594e45; asc WAYNE;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 35 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0022; asc  ";;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b025a; asc     + Z;;
 3: len 6; hex 415544524559; asc AUDREY;;
 4: len 7; hex 4f4c4956494552; asc OLIVIER;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 50 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0031; asc  1;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b02f0; asc     +  ;;
 3: len 4; hex 414e4e45; asc ANNE;;
 4: len 6; hex 43524f4e594e; asc CRONYN;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 66 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0041; asc  A;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b0390; asc     +  ;;
 3: len 6; hex 414e47454c41; asc ANGELA;;
 4: len 6; hex 485544534f4e; asc HUDSON;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 72 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0047; asc  G;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b03cc; asc     +  ;;
 3: len 4; hex 4144414d; asc ADAM;;
 4: len 5; hex 4752414e54; asc GRANT;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 77 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 004c; asc  L;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b03fe; asc     +  ;;
 3: len 8; hex 414e47454c494e41; asc ANGELINA;;
 4: len 7; hex 41535441495245; asc ASTAIRE;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 126 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 007d; asc  ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b05e8; asc     +  ;;
 3: len 6; hex 414c42455254; asc ALBERT;;
 4: len 5; hex 4e4f4c5445; asc NOLTE;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 133 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0084; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b0631; asc     + 1;;
 3: len 4; hex 4144414d; asc ADAM;;
 4: len 6; hex 484f50504552; asc HOPPER;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 145 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0090; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b06b5; asc     +  ;;
 3: len 6; hex 414e47454c41; asc ANGELA;;
 4: len 11; hex 57495448455253504f4f4e; asc WITHERSPOON;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 147 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 0092; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b06cb; asc     +  ;;
 3: len 6; hex 414c42455254; asc ALBERT;;
 4: len 9; hex 4a4f48414e53534f4e; asc JOHANSSON;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 166 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 00a5; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b079c; asc     +  ;;
 3: len 2; hex 414c; asc AL;;
 4: len 7; hex 4741524c414e44; asc GARLAND;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 174 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 00ad; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b07f4; asc     +  ;;
 3: len 4; hex 414c414e; asc ALAN;;
 4: len 8; hex 4452455946555353; asc DREYFUSS;;
 5: len 4; hex 43f23ed9; asc C > ;;

Record lock, heap no 191 PHYSICAL RECORD: n_fields 6; compact format; info bits 0
 0: len 2; hex 00be; asc   ;;
 1: len 6; hex 000000000ef8; asc       ;;
 2: len 7; hex cf0000032b08af; asc     +  ;;
 3: len 6; hex 415544524559; asc AUDREY;;
 4: len 6; hex 4241494c4559; asc BAILEY;;
 5: len 4; hex 43f23ed9; asc C > ;;

从上我们可以看到此事务在表actor上，加上了

mysql> select * from actor where first_name >A and first_name <B for update;
+----------+------------+-------------+---------------------+
| actor_id | first_name | last_name   | last_update         |
+----------+------------+-------------+---------------------+
|       71 | ADAM       | GRANT       | 2006-02-15 04:34:33 |
|      132 | ADAM       | HOPPER      | 2006-02-15 04:34:33 |
|      165 | AL         | GARLAND     | 2006-02-15 04:34:33 |
|      173 | ALAN       | DREYFUSS    | 2006-02-15 04:34:33 |
|      125 | ALBERT     | NOLTE       | 2006-02-15 04:34:33 |
|      146 | ALBERT     | JOHANSSON   | 2006-02-15 04:34:33 |
|       29 | ALEC       | WAYNE       | 2006-02-15 04:34:33 |
|       65 | ANGELA     | HUDSON      | 2006-02-15 04:34:33 |
|      144 | ANGELA     | WITHERSPOON | 2006-02-15 04:34:33 |
|       76 | ANGELINA   | ASTAIRE     | 2006-02-15 04:34:33 |
|       49 | ANNE       | CRONYN      | 2006-02-15 04:34:33 |
|       34 | AUDREY     | OLIVIER     | 2006-02-15 04:34:33 |
|      190 | AUDREY     | BAILEY      | 2006-02-15 04:34:33 |
+----------+------------+-------------+---------------------+
13 rows in set (0.00 sec)| actor | CREATE TABLE `actor` (
  `actor_id` smallint(5) unsigned NOT NULL AUTO_INCREMENT,
  `first_name` varchar(45) NOT NULL,
  `last_name` varchar(45) NOT NULL,
  `last_update` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  PRIMARY KEY (`actor_id`),
  KEY `idx_actor_last_name` (`last_name`),
  KEY `idx_actor_first` (`first_name`)
) ENGINE=InnoDB AUTO_INCREMENT=201 DEFAULT CHARSET=utf8mb4 |

这些行对应的二级索引idx_actor_first加上了X型next_key锁，在对应的聚簇索引上加上了X型record锁

lock_mode X locks gap before rec  表示X型gap锁
lock mode X                       表示X型next_key 锁
lock_mode X locks rec but no gap  表示X型record锁

以上就是mysql查询锁信息的两种方法。

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