- 通過查詢表統計信息查看
information_schema庫下相關事務表和鎖相關信息表介紹
innodb_trx
存儲了當前正在執行的事務信息
trx_id：事務ID。
trx_state：事務狀態，有以下幾種狀態：RUNNING、LOCK WAIT、ROLLING BACK 和 COMMITTING。
trx_started：事務開始時間。
trx_requested_lock_id：事務當前正在等待鎖的標識，可以和 INNODB_LOCKS 表 JOIN 以得到更多詳細信息。
trx_wait_started：事務開始等待的時間。
trx_mysql_thread_id：事務線程 ID，可以和 PROCESSLIST 表 JOIN。
trx_tables_locked：表示該事務目前加了多少個表級鎖。
trx_lock_structs：表示該事務生成了多少個內存中的鎖結構。
trx_lock_memory_bytes：事務鎖住的內存大小，單位為 BYTES。
trx_rows_locked：表示該事務目前加了多少個行級鎖。
innodb_locks
記錄了鎖信息
如果一個事務想要獲取到某個鎖但未獲取到，則記錄該鎖信息
如果一個事務獲取到了某個鎖，但是這個鎖阻塞了別的事務，則記錄該鎖信息
但是無法通過該表查詢到誰被阻塞，誰持有未釋放。
lock_id：鎖 ID。
lock_trx_id：擁有鎖的事務 ID。可以和 INNODB_TRX 表 JOIN 得到事務的詳細信息。
lock_mode：鎖的模式。
lock_type：鎖的類型。RECORD 代表行級鎖，TABLE 代表表級鎖。
lock_table：被鎖定的或者包含鎖定記錄的表的名稱。
innodb_lock_waits
表明每個阻塞的事務是因為獲取不到哪個事務持有的鎖而被阻塞
requesting_trx_id：--獲取不到鎖而被阻塞的事務id（等待方）
requested_lock_id：-- 請求鎖ID ，事務所等待的鎖定的 ID。可以和 INNODB_LOCKS 表 JOIN。
blocking_trx_id： --獲取到別的事務需要的鎖而阻塞其事務的事務id（當前持有方，待釋放）
blocking_lock_id： --這一事務的鎖的 ID，該事務阻塞了另一事務的運行。可以和 INNODB_LOCKS 表 JOIN。
processlist
id:標識ID。這與在SHOW PROCESSLIST語句的Id列、Performance Schema threads表的PROCESSLIST_ID列中顯示的值類型相同，并由CONNECTION_ID()函數返回
user:發出該語句的mysql用戶。
host：發出該語句的客戶機的主機名(系統用戶除外，沒有主機)。
db：默認數據庫。
command：線程正在執行的命令的類型。
time：線程處于當前狀態的時間(以秒為單位)。
state：指示線程正在執行的操作、事件或狀態。
info：線程正在執行的語句，如果沒有執行任何語句，則為NULL。
如何借助這幾張表來定位到有行鎖等待
（1）查看當前有無鎖等待
mysql> show status like 'innodb_row_lock%';
（2）查看哪個事務在等待(被阻塞了)
mysql> select * from information_schema.INNODB_TRX WHERE trx_state='LOCK WAIT'\G
trx_state 表示該事務處于鎖等待狀態。
trx_query : 當前被阻塞的操作是select * from actor where actor_id=1 for update。
從trx_mysql_thread_id和trx_id可以看到這里查到當前被阻塞的事務的：
線程ID是 971，注意說的是線程id
事務ID是3934
（3）查詢該事務被哪個事務給阻塞了 從innodb_trx獲取到被阻塞的trx_id是3934，阻塞該事務的事務id是3933
mysql> SELECT * FROM performance_schema.threads WHERE processlist_id=970\G
（4）根據trx_id，從innodb_trx表可查詢到trx_mysql_thread_id線程id為970
mysql> select * from information_schema.innodb_trx where trx_id=3933 \G
（5）根據線程id，查詢表拿到thread_id為995
mysql> SELECT * FROM performance_schema.threads WHERE processlist_id=970\G
（6）根據thread_id，查詢當前鎖源的sql
mysql> SELECT * FROM performance_schema.events_statements_current WHERE thread_id=995\G
整個流程如下：
（1）首先查詢是否有鎖，根據鎖查到被鎖的trx_id
（2）根據被鎖的trx_id可以查到鎖源的trx_id
（3）根據鎖源的trx_id查到trx_mysql_thread_id（即processlist_id）
（4）再根據trx_mysql_thread_id查到thread_id
（5）最后，用thread_id查找到鎖源的sql
此外，第一步發現鎖的方式，也可直接獲取到鎖源trx_id和被鎖trx_id
但是這種方法在mysql8.0已經被移除，介紹另外一張表
sys.innodb_lock_waits 表
locked_table : 哪張表出現的等待
waiting_trx_id: 等待的事務(與上個視圖trx_id 對應)
waiting_pid : 等待的連接號(與上個視圖trx_mysql_thread_id或processlist_id)
blocking_trx_id : 鎖源的事務ID
blocking_pid : 鎖源的連接號
mysql> select * from sys.innodb_lock_waits\G
獲取到鎖源的blocking_pid 976（=processlist表的id），根據此id找到thread_id，再根據thread_id找到對應的sql
總結：
兩種找到鎖源SQL步驟是一樣的
鎖源的事務trx_id -->pnformaction_schema.processlist表的連接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含義相同
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的應用
1）查看鎖等待相關的（阻塞線程、被阻塞線程信息及相關用戶、IP、PORT、locked_type鎖類型）
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）等待的持續時間（單位秒>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
將鎖信息打印出來
mysql> set global innodb_status_output_locks =ON;
執行如下sql，fisrt_name上有普通二級索引
begin;
select * from actor where first_name >'A' and first_name <'B' for update;
查詢得到該事務ID，方面后面觀察驗證
show engine innodb status看到的事務信息如下
我將注釋寫在#后面
------------
TRANSACTIONS
------------
Trx id counter 3957 #下一個待分配的事務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: #各個事務信息
---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 #事務id為3956的事務，活躍時間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 #事務id為3956的事務，對`sakila`.`actor`加了表級別意向獨占鎖 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 是二級索引，lock_mode X Record lock 表示X型的next_key 鎖
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型記錄鎖
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 > ;;從上我們可以看到此事務在表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 |
這些行對應的二級索引idx_actor_first加上了X型next_key鎖，在對應的聚簇索引上加上了X型record鎖
lock_mode X locks gap before rec 表示X型gap鎖
lock mode X 表示X型next_key 鎖
lock_mode X locks rec but no gap 表示X型record鎖
