Metadata locking is not a replacement for the table definition cache, and its mutexes and locks differ from the LOCK_open mutex. It affects performance. In another article, Valerii introduced performance_schema.metadata_locks, which is available in MySQL 5.7 and exposes metadata lock details.Given this information, here’s a quick way to troubleshoot metadata locks by creating a stored procedure that can: Find out which thread(s) have the metadata lock Reporter: mikeytown2. In a previous article, Ovais demonstrated how a DDL can render a table blocked from new queries. Below is the processlist snapshot. We have tried a few things, and nothing has worked well yet. The server achieves this by acquiring metadata locks on tables used within a transaction and deferring release of those locks until the transaction ends.

Your alter table query hasn't even started. Waiting for table metadata lock: View as plain text : InnoDB question So I have a rename table command that sometimes locks up with the waiting message. Priority: Major. Metadata contention increases the more that multiple queries attempt to access the same objects. | PID 1264 has been waiting for metadata lock on sbtest.sbtest for 264 seconds to execute [truncate table sbtest.sbtest] | 1 row in set ( 0.00 sec) | Other queries waiting for metadata lock | Looking over Waiting for table metadata lock on cache_field table, the earlier patch in #3 gave way to an updated patch in #26. Works perfectly with Mysql 5.1 So I upgraded to 5.5 and now I get an error: "Waiting for table metadata lock" and Info: "Drop table is exists 'component header' " Mysql: Waiting for table metadata lock; Maintain Session across subdomain 2012 (23) December (1) October (1) August (4) July (4) May (2) April (1) March (5) February (3) January (2) 2011 (2) October (2) However, the waiting for table metadata lock means, that there's another transaction operating on that table for a long time and you should rather kill that one to solve the problem. It is often combined with the Needs profiling tag. Category: Bug report. Component: database system. This locking approach has the implication that a table that is being used by a transaction within one session cannot be used in DDL statements by other sessions until the … The server is waiting to acquire a THR_LOCK lock or a lock from the metadata locking subsystem, where lock_type indicates the type of lock. Below is the processlist snapshot.

Metadata locking does involve some overhead, which increases as query volume increases. ** once this happens, even if i kill that thread manually, or it times out (when i set a low lock_timeout) it will always freeze each subsequent time that alter table is issued on that table. the only solution is to kill this stmt. Description: our application is now constantly freezing up and when i look at show processlist, i see only one active statement, and ALTER TABLE ...REORGANIZE PARTITION ... the stmt is in a state of "Waiting for table metadata lock" It never recovers from this and just hangs. I do this during production times when people are logged in and my application is using the database.