Bug #45379 MySQL shouldn't "guess" at the variable names
Submitted: 8 Jun 2009 18:00 Modified: 5 Aug 2015 8:22
Reporter: Sheeri Cabral (Candidate Quality Contributor) Email Updates:
Status: Duplicate Impact on me:
Category:MySQL Server: Options Severity:S4 (Feature request)
Version:5.1.31, 5.0, 5.1, 6.0 bzr OS:Linux
Assigned to: CPU Architecture:Any
Tags: GROUP, group_concat_max_len

[8 Jun 2009 18:00] Sheeri Cabral
On MySQL 5.1.31, with a my.cnf that contains no value for group_concat_max_len, the following warning appears in the MySQL error log when mysqld is restarted:

[Warning] option 'group_concat_max_len': unsigned value 0 adjusted to 4

There is the following variable:


And when that is taken out, the warning doesn't appear.

This means that the value of group_concat_max_len is set to the minimum value (4) when group, an unrelated variable, is set.

How to repeat:
Start up a generic mysqld instance (5.1.31) with no config file

create a config file and add


to the mysqld directive.  restart, and see the problem.

Suggested fix:
MySQL shouldn't "guess" at the variable names -- either it is the right syntax or not.  I suppose this comes about because of variables with names like "sort_buffer" when the variable in mysqld is "sort_buffer_size".

I suggest either honoring the "group" variable or giving an error that it is not a known variable.
[9 Jun 2009 5:19] Sveta Smirnova
Thank you for the report.

Verified as described.
[9 Jun 2009 6:44] MySQL Verification Team
are you sure this is a bug and not just a confusion.  options have always been
recognised by their shortest non-ambiguous versions.  "group=mysql" is actually
seen as "group_concat_max_len=mysql".

since 'mysql' is not a number, it's converted to 0. since 0 is invalid value for group_concat_max_len, it's set to the minimum value of 4.

The problem is customer placed "group=mysql" in [mysqld] section instead of [mysqld_safe].  all this is documented, somewhere in the manual when I checked.
[10 Jun 2009 21:00] Sveta Smirnova

thank you for the hint. You are right - according to http://dev.mysql.com/doc/refman/5.1/en/program-options.html this is not a bug:

An option can be specified by writing it in full or as any unambiguous prefix. For example, the --compress option can be given to mysqldump as --compr
[1 Jul 2009 19:06] Sheeri Cabral
I don't think "group" is unambiguous in this case.
[1 Jul 2009 19:08] Laine Campbell
Saw this too.  Group should not be short for group_concat_max_len.  That's a big risk for potential data corruption, as was just seen with aclient.
[1 Jul 2009 23:21] Arjen Lentz
This is just wrong.
The fact that it's "logical" in the code doesn't make it any more sensible from the outside.

The config parser should not take shorthand, it should only accept full option names.
I realise this might cause issues with people who have been slack, but I have personally not actually seen shorthand being used - people always put in the full option name anyway. Chances are nobody is (consciously) aware of the shorthand ability anyway. And thank goodness for that. Let's get rid of it!
[2 Jul 2009 9:51] Sveta Smirnova
Thank you for the feedback.

If 3 different people ask about removing this feature reclassifying report to feature request with new synopsis.
[27 Jan 2010 21:14] Pavel Stratil
+1 on resolving this feature request.
[28 Jan 2010 2:34] jiang xiaobing
+1 on resolving this feature request.
[15 Apr 2015 3:34] Peter McLarty
+1 for a fix, this is wrong, wrong, wrong. There is no way config files should make, cause, inflict soft changes for options, shorthand be gone.
[15 Apr 2015 5:07] MySQL Verification Team
5.7 fixes this because you can no longer specify short names for variables.

2015-04-15T05:04:56.205775Z 0 [ERROR] unknown variable 'group=mysql'
2015-04-15T05:04:56.206775Z 0 [ERROR] Aborting

Okay to close this FR ?
[22 Jul 2015 12:22] Sascha Nemecek
Can this be backported? We just ran into this issue with a mysqld 5.6.25 installation.
[5 Aug 2015 8:22] Georgi Kodinov
Closing as a duplicate of http://dev.mysql.com/worklog/task/?id=6978.
Unfortunately back-porting this incompatible change to a stable release would cause too much disturbance to existing installations.