Voracious Bug in MySQL
Voracious Bug in MySQL
Written by Kay Ewbank   
Thursday, 12 July 2012

A new version of MySQL has been released by Oracle to correct a bug where MySQL uses all the available disk space when changing a record.

The bug is limited to tables based on MySQL’s InnoDB storage engine.

Hartmut Holzgraefe of SkySQL showed in his blog how the bug can eat the disk space. In a table with two indexes, this SQL uses up all the available space:

UPDATE t1 SET id2 = id2 + 1, b = null 
WHERE a is null and id1 = 2;

What happens is a bit of a mystery, because the InnoDB tablespace expands even though there’s no requirement for extra disk space because of extra data or increased index size.

According to Peter Laursen of Webyog,  there don’t seem to be a lot of options. If innodb_file_per_table is not being used your only choice seems to be to restore to a new server or InnoDB instance having dumped your files.

If you are using innodb_file_per_table option, Lauren suggests that using Optimize Table on the affected tables might free up the disk space that was incorrectly used.

He points out, though, that this still requires there to be enough disk space free to run Optimize Table. Holzgraefe suggests that switching off the index_merge optimizer feature seems to be a viable workaround:

optimizer_switch = 'index_merge=off';

However, the situation is far from ideal. As Laursen points out,

"The lack of willingness of Oracle here to expose the exact conditions for this bug to affected users (and how to repair it should they be affected) is the real problem here".

The new release, MySQL 5.5.25a, does however claim to have resolved the problem.


More Information

Download MySQL 5.5.25a

Related Articles

MySQL 5.5 Now Available


blog comments powered by Disqus


To be informed about new articles on I Programmer, install the I Programmer Toolbar, subscribe to the RSS feed, follow us on, Twitter, Facebook, Google+ or Linkedin,  or sign up for our weekly newsletter.


Udacity Android Design Course Now Live

Udacity's Android Developer Nanodegree was launched at this year's Google I/O and the first cohort of students enrolled in June. The latest Android course on offer is on Material Design and is availab [ ... ]

Apple TV For Developers

Apple has upgraded its set-top box and announced that the future lies in apps. To ensure apps are forthcoming it has launched the tvOS SDK.

More News

Last Updated ( Saturday, 21 July 2012 )

RSS feed of news items only
I Programmer News
Copyright © 2015 i-programmer.info. All Rights Reserved.
Joomla! is Free Software released under the GNU/GPL License.