How do I reduce the size of mlocate database?

The /var/lib/mlocate/mlocate.db.?????? files are leftover temporary files from a (probably) interrupted updatedb run. They don't appear on either of my Ubuntu 11.10 systems, except when updatedb is running. Delete them:

sudo rm -f /var/lib/mlocate/mlocate.db.??????

then, to be sure, run

sudo /etc/cron.daily/mlocate