EmergencyEMERGENCY? Get 24/7 Help Now!

MySQL and predictive option handling – beware

Posted on:



Share Button

MySQL command line utilities have an interesting property – if you only use the prefix of the option or command it will go over the list of available command and if there is only one command with matching prefix it will execute it with no warnings or any kind, otherwise it will report the error. For example mysqladmin e works as there is only one command “extended-status” which starts with “e” mysqladmin f however does not work because there are multiple commands which start with “f”.

This behavior can cause all kings of issues especially if you make a typo. I made one today (thankfully on the test box). MySQL init Scripts use “stop” and “start” commands to start and stop the server while mysqladmin uses “shutdown”. I mixed this while trying to stop Percona Server:

It would be quite confusing if mysqladmin would have “stop” command which does not do the same thing as “shutdown” . And it does not. The commands it has are
“start-slave” and “stop-slave” though as these are the only commands with such prefixes they are matched to “start” and “stop” appropriately.

I think such automated option prediction is very dangerous and it gets more dangerous the more options are added for the tools as it is more likely your mistake can be actually matching something… I think much better solution would be to have explicitly created synonyms and shortcuts if they are needed. For example “extended-status” is rather option and we can allow “extended” shortcut for it or might be even “ext” but allowing “e” is an overkill.

Share Button

Peter Zaitsev

Peter managed the High Performance Group within MySQL until 2006, when he founded Percona. Peter has a Master's Degree in Computer Science and is an expert in database kernels, computer hardware, and application scaling.

Insight for DBAs, MySQL


Leave a Reply

Percona’s widely read Percona Data Performance blog highlights our expertise in enterprise-class software, support, consulting and managed services solutions for both MySQL® and MongoDB® across traditional and cloud-based platforms. The decades of experience represented by our consultants is found daily in numerous and relevant blog posts.

Besides specific database help, the blog also provides notices on upcoming events and webinars.

Want to get weekly updates listing the latest blog posts? Subscribe to our blog now! Submit your email address below.

No, thank you. Please do not ask me again.