How to catch database exception and not display it to browser

[eluser]chandrajatnika[/eluser]
In CodeIgniter, how to catch exception from query error or other database error, so I can customize exception behaviour like save it to log file or anything. And error that occured didn't displayed on browser, just a white blank or an error page without error description.

I've tried to create MY_DB_driver to overwrite CI_DB_driver display_error function, but I didn't work because CI_DB_driver is called from CI_Loader. I think it's to complicated for a simple job like this.
Could you tell me the easiest way to do this?

Regards