- 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（即processlist_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 : 等待的连接号(与上个视图trx_mysql_thread_id或processlist_id)
blocking_trx_id : 锁源的事务id
blocking_pid : 锁源的连接号
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表的连接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