MySQL Transaction--查看未提交事务执行的SQL

Posted 2021-11-03 gaogao67

未提交事务

长期未提交事务，指开启事务后，长时间未向mysql发出SQL执行请求或事务处理(COMMIT/ROLLBACK)请求，在系统表`information_schema`.`INNODB_TRX` 中状态为RUNNING，而在`information_schema`.`PROCESSLIST`中状态为SlEEP。

## 查看未提交的事务(3秒内未操作的事务)
SELECT 
p.ID AS conn_id,
P.USER AS login_user,
P.HOST AS login_host,
p.DB AS database_name,
P.TIME AS trx_sleep_seconds,
TIME_TO_SEC(TIMEDIFF(NOW(),T.trx_started)) AS trx_open_seconds,
T.trx_started,
T.trx_isolation_level,
T.trx_tables_locked,
T.trx_rows_locked,
t.trx_state,
p.COMMAND AS process_state
FROM `information_schema`.`INNODB_TRX` t
INNER JOIN `information_schema`.`PROCESSLIST` p
ON t.trx_mysql_thread_id=p.id
WHERE t.trx_state=‘RUNNING‘
AND p.COMMAND=‘Sleep‘
AND P.TIME>3
ORDER BY T.trx_started ASC \G

 

导致事务长期未提交的因素很多，常见的有：

1、事务过程中执行其他非数据库操作，导致事务长期未被处理。
2、事务处理异常或实现逻辑有误，导致事务未被正常处理。
3、网段异常导致应用端请求未被正常发送给数据库，数据库等待应用后续操作。
4、应用服务器性能问题(如CPU爆满)，导致应用无法及时切换到该进程进行处理。

 

对于代码实现逻辑有误的问题，如果DBA能提供该事务执行的SQL语句将有助于研发快递定位，哪如何定位呢？

方式1：使用通用日志

## 查看general log配置
show variables like ‘%general_log%‘

## 开启general log
SET GLOBAL general_log = 1;

在通用日志中能看到

2019-04-29T13:52:07.932646+08:00    20036 Query    SELECT * FROM `sys`.`processlist`
2019-04-29T13:52:36.049694+08:00    20036 Query    SELECT * FROM `sys`.`processlist` WHERE CONN_ID=2036
2019-04-29T13:52:44.378687+08:00    20036 Query    SELECT * FROM `sys`.`processlist` WHERE CONN_ID=20040
2019-04-29T13:52:51.418669+08:00    20036 Query    SELECT * FROM `sys`.`processlist` WHERE CONN_ID=20040

上面的20036是会话连接号(connection id), 使用SHOW PROCESSLIST 或`information_schema`.`PROCESSLIST`查到的ID即该ID。

 

对于MySQL 5.7版本，可以使用sys.session视图来查看会话最后一次执行的SQL：

SELECT * 
FROM sys.session 
WHERE CONN_ID = 20036 \G

输出结果为：

            thd_id: 20065
           conn_id: 20040
              user: [email protected]172.28.37.35
                db: demodb
           command: Sleep
             state: NULL
              time: 19
 current_statement: NULL
 statement_latency: NULL
          progress: NULL
      lock_latency: 157.00 us
     rows_examined: 110
         rows_sent: 110
     rows_affected: 0
        tmp_tables: 0
   tmp_disk_tables: 0
         full_scan: YES
    last_statement: select * from tb001 limit 110
last_statement_latency: 607.34 us
    current_memory: 0 bytes
         last_wait: NULL
 last_wait_latency: NULL
            source: NULL
       trx_latency: NULL
         trx_state: NULL
    trx_autocommit: NULL
               pid: 12758
      program_name: mysql

 

使用系统视图sys.processlist 也能看到类似上面的结果：

SELECT *  
FROM sys.processlist 
WHERE CONN_ID = 20040

 

系统视图sys.processlist中数据主要来源于：

performance_schema.events_statements_current
performance_schema.events_statements_history

且上面两个表中记录的数据需要使用线程号(THREAD ID)，可以使用performance_schema.threads来与连接号(CONNECTION ID/PROCESSLIST ID)进行关联。

 

因此可以将查询未提交事务的SQL优化为：

## 查看未提交的事务(3秒内未操作的事务)
SELECT 
p.ID AS conn_id,
P.USER AS login_user,
P.HOST AS login_host,
p.DB AS database_name,
P.TIME AS trx_sleep_seconds,
TIME_TO_SEC(TIMEDIFF(NOW(),T.trx_started)) AS trx_open_seconds,
T.trx_started,
T.trx_isolation_level,
T.trx_tables_locked,
T.trx_rows_locked,
t.trx_state,
p.COMMAND AS process_state,
(
SELECT GROUP_CONCAT(T1.`SQL_TEXT` SEPARATOR ‘;
‘) 
FROM performance_schema.events_statements_history AS T1
INNER JOIN performance_schema.threads AS T2
ON T1.`THREAD_ID`=T2.`THREAD_ID`
WHERE T2.`PROCESSLIST_ID`=P.id
) AS trx_sql_text
FROM `information_schema`.`INNODB_TRX` t
INNER JOIN `information_schema`.`PROCESSLIST` p
ON t.trx_mysql_thread_id=p.id
WHERE t.trx_state=‘RUNNING‘
AND p.COMMAND=‘Sleep‘
AND P.TIME>3
ORDER BY T.trx_started ASC \G

输出结果中trx_sql_text即该事务执行过的SQL语句。