[mythtv-users] MySQL related BE deadlocks - collective wisdom needed

[Michael T. Dean]

On 07/25/2011 02:22 PM, Warpme wrote:
> Mike,
>
> Pls find attached BE trace &  SHOW ENGINE INNODB STATUS\G from 
> deadlocked BE (protocol version check deadlock).

This is SHOW ENGINE INNODB STATUS while it's deadlocked?

> Regarding mythshutdown - no I'm not using it at all.
> When I'm shutting or rebooting server - SIGTERM is used (I'm using 
> systemd as replacement to SysV init). But I have to admit - many BE 
> shutdowns are ended with segfaults.
> Your previous post suggests switch to InnoDB wasn't good idea. May You 
> elaborate why ?
> Should I switch back to MyISAM ?

I'm saying that we will eventually switch all schemas to InnoDB.  In 
general we recommend users never modify any of the schema since parts of 
MythTV may be written to assume certain schema configuration (such as 
all the places that do SELECT COUNT(), which is very fast on MyISAM but 
rather inefficient on InnoDB), or future updates to the MythTV schema 
may fail if your schema is not the one we expect (the one we created), 
thereby preventing a smooth upgrade.  It's the old, "If you're modifying 
our data and things break (now or at any time in the future) as a 
result, you get to clean up the mess."

More than anything I wanted to make sure we don't have a bunch of users 
who are seeing backend deadlocks start trying to convert to InnoDB, 
thinking that would fix the problem.

Whether you switch back or not is up to you--but since you're already on 
InnoDB, please try to get the InnoDB status while it's locked before 
doing so, if the one you sent wasn't while it was locked.

Thanks,
Mike