So… Baron blogged about wanting higher precision timers from the mysql binary and that running sed on the binary wasn’t cutting it. However… I am not one to give up that easily!
This is what LD_PRELOAD was made for! Evil nasty hacks to make your life easier!
By looking at the mysql.cc source code, I can easily work out how this works… I just have to override two calls! They being sysconf() (we fake how many ticks per second there are) and times() (let’s return a much higher precision number).
Combined with the sed hack on the binary to change the sprintf call to print out the higher precision number, we have:
mysql> select count(*) from t1; +----------+ | count(*) | +----------+ | 710720 | +----------+ 1 row in set (1.080110 sec)
Get it from my junkcode: http://www.flamingspork.com/junkcode/high_precision_mysql_timer.c
(or you can get it from http://paste.drizzle.org/show/364/)
Pingback: Tweets that mention Timing queries in the 21st century (with LD_PRELOAD and sed) | Ramblings -- Topsy.com
Muah hah hah!!!
Great and … nasty! :-)
I was jut thinking about something similar the other day; is it possible, to hijack all mysql c/c++ functions this way?
For example (file)sort?
BTW how leagal is this? :-)
perfectly legal. You can override a lot of things using LD_PRELOAD, but really, with software you have the source for – it’s best to fix it.
Add the following to your instructions, there are a lot of people out there that will need the help.
chmod +x ./mysql-fixed
And I’d suggest this.
sed -e ‘s/%\.2f sec/%.6f sec/’ `which mysql` > mysql-fixed
true, the better sed expression probably works better.
and let me be just a tiny bit scared that people may end up using this…
Pingback: Book Review - Effective MySQL | iHeavy blog