maria-discuss team mailing list archive

[Ian Gilfillan <ian@xxxxxxxxxxx>]

On 01/01/2015 06:13 PM, Federico Razzoli wrote:
> Morgan Tocker asked the community's opinions about SHOW ENGINE INNODB MUTEX:
> http://www.tocker.ca/2013/11/28/show-engine-innodb-mutex.html
>
> Despite these opinions, as Valerii Kravchuk notes on Facebook, the command disappeared in the latest 5.7 release. He also notes that the command has never been deprecated (!).
>
> Question is: will MariaDB preserve this command? Frankly, I don't know any other convenient way to obtain the same information...
The main reason in favour of its removal in MySQL seems to be this point:

"The InnoDB mutex code was recently refactored as part of our server 
cleanup. After refactoring, the InnoDB code can now mix several mutex 
types internally including spin locks, system mutexes (POSIX) and InnoDB 
home brewed ones. The display output for |SHOW ENGINE INNODB MUTEX| 
doesn't really account for these differences in its status column. 
Grouping all mutex types together becomes less intuitive, and would 
require either some change to the output, or a coarse (inaccurate) 
mixing of the types:"

The performance schema however is less intuitive to use, and, as was 
noted in the MySQL announcement of the removal, doesn't yet include 
spinning information.

There's a post on Percona's blog that looks at getting similar 
information using the Performance Schema:
http://www.percona.com/blog/2015/01/06/getting-mutex-information-from-mysqls-performance_schema/

Much depends on what happens with XtraDB's implementation, but I 
wouldn't be in favour of just removing it without notice, as happened in 
MySQL 5.7. It should at least be deprecated.

ian