Why there is not bug fix in GA version


Reporter of bug #44604 pointed to common problem: "Why don't backport bugfix to previous major version?" Especially if this version is GA.


This particular bug seems to be fixed by redesign of MySQL Optimizer which was dramatically improved in version 6.0


At the same time while some feature is improved in new version backport this improvement or even part of it into older one is not easy and can lead to instability or affect other applications. There is always balance between risk and effort to fix.


Same reasons apply for other bugs in similar state.


Of course this applies only to bugs with good workaround or to rare cases and should never apply to crashing bugs. While sometime is not easy to properly fix crashing bug in stable version. Example of such a bug were bug #37846 and bug #37847 Real fix for version 5.0 contained message in error log instead of crash while in 5.1 error doesn't occur at all.

Comments:

I prefer that major optimizer changes not show up in the middle of a GA, but more frequent releases of major versions of MySQL makes this easier to tolerate. At times my attitude is even more extreme and I want most/many optimizer changes to have a flag that allows me to disable them.

Fortunately, the MySQL optimizer rarely causes problems for me. Rapidly changing query plans caused by rapidly changing Innodb table statistics are a different matter.

Posted by Mark Callaghan on June 02, 2009 at 12:32 PM MSD #

I believe Optimizer developers agree with you since we have system variable optimizer_switch since 5.1.34, some improvements planned in frame of http://forge.mysql.com/worklog/task.php?id=4046

Having optimizer bug fix turn on/off switches can be good. There even were discussion about this, but at the other side there could be new problems such as "how to find a reason for a crush or wrong behavior" or "how to tune server correctly for not very experienced users" if many new switches are introduced.

Posted by Sveta Smirnova on June 03, 2009 at 04:56 AM MSD #

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Working blog of Sveta Smirnova - MySQL Senior Principal Support Engineer working in Bugs Analysis Support Group

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