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