https://groups.google.com/d/topic/security-onion/qcDgy0Meh5M/discussion

As a band-aid, I added the following code to the beginning of the cleanup() 
function in the sguil-db-purge script:

/usr/bin/mysql -u$DB_USER $PASSWORD_OPTION -BN -e "DELETE FROM history WHERE 
timestamp < DATE_SUB(NOW(), INTERVAL 90);" -D $DATABASE

This should keep a rolling 90-day history and speed up any upgrades/maintenance.

Added the following:

        /usr/bin/mysql -u$DB_USER $PASSWORD_OPTION -BN -e "DELETE FROM history WHERE timestamp < DATE_SUB(NOW(), INTERVAL $DAYSTOKEEP DAY);" -D $DATABASE

Submitted for testing:
https://groups.google.com/d/topic/security-onion-testing/Wy55RCCpsvc/discussion

Published:
http://blog.securityonion.net/2014/06/new-securityonion-sguil-db-purge.html