【0】核心表
sys.`innodb_lock_waits`
performance_schema.events_statements_history
performance_schema.data_locks
performance_schema.data_locks_wait
【1】查看鎖信息
performance_schema.data_locks
performance_schema.data_locks_wait
線上mysql版本為8.0.11，對於最近的幾個版本越來越像Orale了，有了較為豐富的系統字典，也可以查看系統的等待事件，現在線上出現被鎖語句的情況也可以通過數據字典直接查詢出來了，在此記錄下以供參考。
首先查看系統鎖情況，下面這條語句可以看到持有鎖的線程以及線程ID，這里需要注意下，session_id也就是show processlist查詢出來的鏈接ID，在這個表里表現為PID，同時該表也記錄了trx_id，最后還給出了解決方案也就是如何kill持有鎖的進程。
mysql> SELECT * FROM sys.`innodb_lock_waits` \G *************************** 1. row *************************** wait_started: 2019-01-28 14:27:03 wait_age: 00:00:03 wait_age_secs: 3 locked_table: `test`.`t` locked_table_schema: test locked_table_name: t locked_table_partition: NULL locked_table_subpartition: NULL locked_index: GEN_CLUST_INDEX locked_type: RECORD waiting_trx_id: 19758723 waiting_trx_started: 2019-01-28 14:27:03 waiting_trx_age: 00:00:03 waiting_trx_rows_locked: 1 waiting_trx_rows_modified: 0 waiting_pid: 4202 waiting_query: update t set id=8 waiting_lock_id: 19758723:4998:4:2 waiting_lock_mode: X blocking_trx_id: 19748728 blocking_pid: 4200 blocking_query: NULL blocking_lock_id: 19748728:4998:4:2 blocking_lock_mode: X blocking_trx_started: 2019-01-28 10:58:27 blocking_trx_age: 03:28:39 blocking_trx_rows_locked: 2 blocking_trx_rows_modified: 1 sql_kill_blocking_query: KILL QUERY 4200 sql_kill_blocking_connection: KILL 4200 1 row in set (0.02 sec
【2】查看當前被鎖的語句
##等待鎖的語句 SELECT * FROM performance_schema.events_statements_history WHERE thread_id IN( SELECT b.`THREAD_ID` FROM sys.`innodb_lock_waits` AS a , performance_schema.threads AS b WHERE a.waiting_pid = b.`PROCESSLIST_ID`) ORDER BY timer_start ASC;
【3】看持有鎖的語句
可以通過如下方式
##持有鎖的語句 SELECT * FROM performance_schema.events_statements_history WHERE thread_id IN( SELECT b.`THREAD_ID` FROM sys.`innodb_lock_waits` AS a , performance_schema.threads AS b WHERE a.`blocking_pid` = b.`PROCESSLIST_ID`) ORDER BY timer_start ASC;
