Better visibility of metadata locks

Registered by Ovais Tariq on 2013-03-27

I was also wondering about the possibility of having a new table in I_S database in the Percona Server, that could show the current metadata locks being held by a transaction, quite similar to INNODB_LOCKS table. This is because currently there is no direct way to find out which transaction is holding the metadata locks that are blocking a DDL and that makes metadata locking difficult to diagnose if there are a lot of sleeping transactions.

MySQL 5.7.3 implements wait/lock/metadata/sql/mdl, see e.g. http://www.chriscalender.com/tracking-metadata-locks-mdl-in-mysql-5-7/. -Laurynas

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Oracle implementation in 5.7.3: https://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-3.html ("The Performance Schema now exposes metadata lock information: ...").

MariaDB implementation in 10.0.7: https://mariadb.com/kb/en/metadata-lock-info/

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