MYSQL MDL监控

MYSQL5.7以上才支持

Enable:

UPDATE performance_schema.setup_instruments
SET ENABLED = 'YES', TIMED = 'YES'
WHERE NAME = 'wait/lock/metadata/sql/mdl';


Disable:

UPDATE performance_schema.setup_instruments
SET ENABLED = 'NO', TIMED = 'NO'
WHERE NAME = 'wait/lock/metadata/sql/mdl';

每个线程持有的MDL锁在metadata_locks表有详情：

SELECT * FROM performance_schema.metadata_locks

参考文档：https://dev.mysql.com/doc/refman/5.7/en/performance-schema-metadata-locks-table.html