实战篇（如何查看mysql里面的锁） _如何

大鹏一日同风起，扶摇直上九万里。这篇文章主要讲述实战篇：如何查看mysql里面的锁相关的知识，希望能为你提供帮助。

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&
gt;
 show status like innodb_row_lock%;

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（2）查看哪个事务在等待(被阻塞了)

mysql&
gt;
 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：
【实战篇（如何查看mysql里面的锁）】线程ID是 971，注意说的是线程id
事务ID是3934

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（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&
gt;
 SELECT * FROM performance_schema.threads WHERE processlist_id=970\\G

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

mysql&
gt;
 select * from information_schema.innodb_trx where trx_id=3933 \\G

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（5）根据线程id，查询表拿到thread_id为995

mysql&
gt;
 SELECT * FROM performance_schema.threads WHERE processlist_id=970\\G

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（6）根据thread_id，查询当前锁源的sql

mysql&
gt;
 SELECT * FROM performance_schema.events_statements_current WHERE thread_id=995\\G

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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

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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&
gt;
 select * from sys.innodb_lock_waits\\G

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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

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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;

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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&
gt;
 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 &
gt;
A and first_name &
lt;
B for update;
<
br/>
查询得到该事务ID，方面后面观察验证<
br/>

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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; ascG; ; 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; ascA; ; 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; ascL; ; 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; asc1; ; 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; asc1; ; 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; ascA; ; 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; ascG; ; 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; ascL; ; 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