Comments on: Debugging metadata locking in MySQL 5.5

By: Sheeri K. Cabral

Sheeri K. Cabral — Thu, 06 Sep 2012 20:11:07 +0000

Would it be possible for pt-deadlock-logger to store this information too? (or is that where it gets it?) I’ve enjoyed using it but it only explains one of the 2 locks that cause the deadlock :(

By: Daniël van Eeden

Daniël van Eeden — Mon, 03 Sep 2012 05:34:12 +0000

Maybe watching open files with lsof could give some hints about what’s going on?
It could also be hardware/OS related. (full filesystem, out of memory, SSD firmware bug, etc)

By: Normann

Normann — Tue, 28 Aug 2012 18:43:47 +0000

if i kill a huge insert qry, I get a “Waiting for table metadata lock” too. but the connection status is just “killed”

By: Xaprb

Xaprb — Tue, 28 Aug 2012 18:02:09 +0000

I have a feeling something like this is the problem in my case too.

By: sbester

sbester — Tue, 28 Aug 2012 17:34:49 +0000

one that is particularly tricky to diagnose when innodb table is not involved. e.g.

conn1: begin;
conn1: select * from myisam_table;
conn2: drop table myisam_table;

conn2 will simply hang until lock_wait_timeout expires and there’s no easy way to know that conn1 is responsible.