← Back to team overview

maria-developers team mailing list archive

Re: prefix matching for command-line options - how to disable?


Hi, Jean!

On Jan 06, Jean Weisbuch wrote:
> Indeed, its a really annoying behavior that can lead to bad surprises 
> and similar issues can happen with command line tools that also supports 
> abbreviations such as the mysql CLI, mysqladmin or mysqldump (eg: 
> MDEV-7208).
> > 1. support a special suffix to option names that will disable prefix
> >     matching, for example:
> >      mysqld --enable-innodb-buffer-page!
> >
> The first solution, to put a prefix/suffix on options would break 
> compatibility with MySQL and other derivatives and add another level of 
> complexion that most of the users wont even bother try to understand.

It will break compatibility with 5.7 (because 5.7 doesn't do prefix
matching), but it'll be perfectly compatible with 5.6 and earlier
versions, because '!' was invalid on the command line, so adding new
semantics for it doesn't introduce incompatibilities. And it's
compatible with existing my.cnf files.

But I agree about complexity, I don't like that either.

> > 2. add a special command-line option to disable prefix matching:
> >      mysqld --disable-getopt-prefix-matching --enable-innodb-buffer-page
> >
> The second solution seems the best to me : i think that such an option
> should be added even on 10.0 and even if it would be disabled by
> default on 10.0, there should be at least a warning throwed when an
> abbreviation is used telling how it was really interpreted and that
> abbreviation use is not recommended/deprecated ; that option would be
> enabled by default on 10.1 or at least this option would be enabled on
> the default/example my.cnf files supplied with MariaDB so it wouldnt
> break existing setups and could be disabled for peoples that wants to
> stick with their bad habits.

Okay, thanks. It feels a bit strange to control command line option
parsing with a command line option. But it'll work.

> > 3. do like mysql-5.7 is doing and completely remove support for
> > prefix matching. In 5.7 one has to specified option names in full. I
> > suspect that this is likely to break many exising setups.
> >
> The third solution makes sense if the second one requires much work to
> be implemented and doesnt seems to be that important, a simple
> deprecation warning for abbreviated commands on 10.0 would do the
> trick then but i suspect that doing that, does takes almost as
> implementing solution #2.
> ps: i never used abbreviations and never saw configurations or users
> using them (on purpose at least).

Yes, I don't think that many use that on purpose. But they're easy to
use unintentionally. Like one writes max-length-for-sort=2K and that
works, so he believes that's the correct option name (while in fact it's
max-length-for-sort-data). Or myisam-recover=FORCE. It's even documented
in the manual as "myisam-recover", while the correct full name is