技术分享 | 怎么找到上锁的 SQL 语句|mysql|query|schema|sql

作者：岳明强
爱可生北京分公司 DBA 团队成员，负责数据库管理平台的运维和 MySQL 问题处理。擅长对 MySQL 的故障定位。
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问题

有的时候 SQL 语句被锁住了，可是通过 show processlist 找不到加锁的的 SQL 语句，这个时候应该怎么排查呢

前提

performance_schema = on;

实验

1、建一个表，插入三条数据

mysql> use test1; Database changed mysql> create table action1(id int); Query OK, 0 rows affected (0.11 sec) mysql> insert into action1 values(1),(2),(3); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> select * from action1; +------+ | id | +------+ | 1 | | 2 | | 3 | +------+ 3 rows in set (0.00 sec)

2、开启一个事务，删除掉一行记录，但不提交mysql> begin; Query OK, 0 rows affected (0.00 sec) mysql> delete from action1 where id = 3; Query OK, 1 row affected (0.00 sec)

3、另开启一个事务，更新这条语句，会被锁住

mysql> update action1 set id = 7 where id = 3; 4、通过 show processlist 只能看到一条正在执行的 SQL 语句

5、接下来就是我们知道的，通过 information_schema 库里的 INNODBTRX、INNODBLOCKS 、INNODBLOCK_WAITS 获得的一个锁信息

mysql> select * from INNODB_LOCK_WAITS; +-------------------+-------------------+-----------------+------------------+ | requesting_trx_id | requested_lock_id | blocking_trx_id | blocking_lock_id | +-------------------+-------------------+-----------------+------------------+ | 5978292 | 5978292:542:3:2 | 5976374 | 5976374:542:3:2 | +-------------------+-------------------+-----------------+------------------+ 1 row in set, 1 warning (0.00 sec) mysql> select * from INNODB_LOCKs; +-----------------+-------------+-----------+-----------+-------------------+-----------------+------------+-----------+----------+----------------+ | lock_id | lock_trx_id | lock_mode | lock_type | lock_table | lock_index | lock_space | lock_page | lock_rec | lock_data | +-----------------+-------------+-----------+-----------+-------------------+-----------------+------------+-----------+----------+----------------+ | 5978292:542:3:2 | 5978292 | X | RECORD | `test1`.`action1` | GEN_CLUST_INDEX | 542 | 3 | 2 | 0x00000029D504 | | 5976374:542:3:2 | 5976374 | X | RECORD | `test1`.`action1` | GEN_CLUST_INDEX | 542 | 3 | 2 | 0x00000029D504 | +-----------------+-------------+-----------+-----------+-------------------+-----------------+------------+-----------+----------+----------------+ 2 rows in set, 1 warning (0.00 sec) mysql> select trx_id,trx_started,trx_requested_lock_id,trx_query,trx_mysql_thread_id from INNODB_TRX; +---------+---------------------+-----------------------+----------------------------------------+---------------------+ | trx_id | trx_started | trx_requested_lock_id | trx_query | trx_mysql_thread_id | +---------+---------------------+-----------------------+----------------------------------------+---------------------+ | 5978292 | 2020-07-26 22:55:33 | 5978292:542:3:2 | update action1 set id = 7 where id = 3 | 22226 | | 5976374 | 2020-07-26 22:47:33 | NULL | NULL | 22188 | +---------+---------------------+-----------------------+----------------------------------------+---------------------+

6、从上面可以看出来是 thread_id 为 22188 的执行的 SQL 语句锁住了后面的更新操作，但是我们从上文中 show processlist 中并未看到这条事务，测试环境我们可以直接 kill 掉对应的线程号，但如果是生产环境中，我们需要找到对应的 SQL 语句，根据相应的语句再考虑接下来应该怎么处理。

7、需要结合 performance_schema.threads 找到对应的事务号

mysql> select * from performance_schema.threads where processlist_ID = 22188\G *************************** 1. row *************************** THREAD_ID: 22225 //perfoamance_schema中的事务计数器 NAME: thread/sql/one_connection TYPE: FOREGROUND PROCESSLIST_ID: 22188 //从show processlist中看到的id PROCESSLIST_USER: root PROCESSLIST_HOST: localhost PROCESSLIST_DB: test1 PROCESSLIST_COMMAND: Sleep PROCESSLIST_TIME: 1527 PROCESSLIST_STATE: NULL PROCESSLIST_INFO: NULL PARENT_THREAD_ID: NULL ROLE: NULL INSTRUMENTED: YES HISTORY: YES CONNECTION_TYPE: Socket THREAD_OS_ID:8632 1 row in set (0.00 sec)

8、找到事务号，可以从 events_statements_current 找到对应的 SQL 语句：SQL_TEXT

mysql> select * from events_statements_current where THREAD_ID = 22225\G *************************** 1. row *************************** THREAD_ID: 22225 EVENT_ID: 14 END_EVENT_ID: 14 EVENT_NAME: statement/sql/delete SOURCE: TIMER_START: 546246699055725000 TIMER_END: 546246699593817000 TIMER_WAIT: 538092000 LOCK_TIME: 238000000 SQL_TEXT: delete from action1 where id = 3 //具体的sql语句 DIGEST: 8f9cdb489c76ec0e324f947cc3faaa7c DIGEST_TEXT: DELETE FROM `action1` WHERE `id` = ? CURRENT_SCHEMA: test1 OBJECT_TYPE: NULL OBJECT_SCHEMA: NULL OBJECT_NAME: NULL OBJECT_INSTANCE_BEGIN: NULL MYSQL_ERRNO: 0 RETURNED_SQLSTATE: 00000 MESSAGE_TEXT: NULL ERRORS: 0 WARNINGS: 0 ROWS_AFFECTED: 1 ROWS_SENT: 0 ROWS_EXAMINED: 3 CREATED_TMP_DISK_TABLES: 0 CREATED_TMP_TABLES: 0 SELECT_FULL_JOIN: 0 SELECT_FULL_RANGE_JOIN: 0 SELECT_RANGE: 0 SELECT_RANGE_CHECK: 0 SELECT_SCAN: 0 SORT_MERGE_PASSES: 0 SORT_RANGE: 0 SORT_ROWS: 0 SORT_SCAN: 0 NO_INDEX_USED: 0 NO_GOOD_INDEX_USED: 0 NESTING_EVENT_ID: NULL NESTING_EVENT_TYPE: NULL NESTING_EVENT_LEVEL: 0 1 row in set (0.00 sec)