MySQL Bugs: #45379: MySQL shouldn't "guess" at the variable names

Bug #45379	MySQL shouldn't "guess" at the variable names
Submitted:	8 Jun 2009 20:00	Modified:	2 Jul 2009 11:51
Reporter:	Sheeri Cabral (Candidate Quality Contributor)	Email Updates:
Status:	Verified
Category:	Server: Options	Severity:	S4 (Feature request)
Version:	5.1.31, 5.0, 5.1, 6.0 bzr	OS:	Linux
Assigned to:		Target Version:
Tags:	GROUP, group_concat_max_len
Triage:	Needs Triage: D5 (Feature request)

Description:
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:

group=mysql

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

group=mysql

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.

Thank you for the report.

Verified as described.

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.

Shane,

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

I don't think "group" is unambiguous in this case.

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.

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!
Thanks

Thank you for the feedback.

If 3 different people ask about removing this feature reclassifying report to feature
request with new synopsis.

+1 on resolving this feature request.

+1 on resolving this feature request.