MySQL锁表相关问题查找思路

默认使用INNODB存储引擎，查询当前是否有锁表情况

select * from information_schema.INNODB_LOCK_WAITS;
select * from information_schema.INNODB_LOCKS;

查看事务等待状况

SELECT
     r.trx_id waiting_trx_id,
     r.trx_mysql_thread_id waiting_thread,
     r.trx_query waiting_query,
     b.trx_id blocking_trx_id,
     b.trx_mysql_thread_id blocking_thread,
     b.trx_query blocking_query
FROM
     information_schema.innodb_lock_waits w
INNER JOIN information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id
INNER JOIN information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id;

查看更具体的事务等待状况

SELECT
     b.trx_state,
     e.state,
     e.time,
     d.state AS block_state,
     d.time AS block_time,
     a.requesting_trx_id,
     a.requested_lock_id,
     b.trx_query,
     b.trx_mysql_thread_id,
     a.blocking_trx_id,
     a.blocking_lock_id,
     c.trx_query AS block_trx_query,
     c.trx_mysql_thread_id AS block_trx_mysql_tread_id
FROM
     information_schema.INNODB_LOCK_WAITS a
LEFT JOIN information_schema.INNODB_TRX b ON a.requesting_trx_id = b.trx_id
LEFT JOIN information_schema.INNODB_TRX c ON a.blocking_trx_id = c.trx_id
LEFT JOIN information_schema.PROCESSLIST d ON c.trx_mysql_thread_id = d.id
LEFT JOIN information_schema.PROCESSLIST e ON b.trx_mysql_thread_id = e.id
ORDER BY
     a.requesting_trx_id;

开启 general log 查询锁表事务内语句

SHOW VARIABLES LIKE 'general_log%';

set GLOBAL general_log = on; #开启
set GLOBAL general_log = off; #关闭
set global log_output='table'; #设置输出方式为表
-- 根据上述查询出来的thread_id
SELECT * from mysql.general_log WHERE thread_id = 441;

注意：general log会记录所有的sql语句，调试过程中，找到自己需要的sql后及时关闭，否则会造出空间不足。

查看未关闭的事务（ MySQL 5.6及以上）

SELECT
     a.trx_id,
     a.trx_state,
     a.trx_started,
     a.trx_query,
     b.ID,
     b.USER,
     b.DB,
     b.COMMAND,
     b.TIME,
     b.STATE,
     b.INFO,
     c.PROCESSLIST_USER,
     c.PROCESSLIST_HOST,
     c.PROCESSLIST_DB,
     d.SQL_TEXT
FROM
     information_schema.INNODB_TRX a
LEFT JOIN information_schema.PROCESSLIST b ON a.trx_mysql_thread_id = b.id
AND b.COMMAND = 'Sleep'
LEFT JOIN PERFORMANCE_SCHEMA.threads c ON b.id = c.PROCESSLIST_ID
LEFT JOIN PERFORMANCE_SCHEMA.events_statements_current d ON d.THREAD_ID = c.THREAD_ID;