If using Sphinx, you need to refresh indexes when you add new content to your database. This is fairly easy to do by hand

rake thinking_sphinx:index RAILS_ENV=production

But if you want to automate this and use a cron, remember to set the PATH, SHELL and RAILS_ENV variables for your job. The environment isn't the same when you're doing it by hand and your index will fail silently :(

You find your specific PATH and SHELL info like so

echo $PATH
echo $SHELL

To get into the cron and set your schedule

crontab -e

PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
SHELL=/bin/bash
RAILS_ENV=production
re-index production sphinx every 15 minutes
/15    * root cd /var/www/rails_app && /usr/local/bin/rake thinking_sphinx:index >> /dev/null 2>&1

More information available here http://heimdull.blogspot.com/2009/05/journey-with-thinking-sphinx-and-crond.html http://groups.google.com/group/thinking-sphinx/browse_thread/thread/5451458fae7d6124

Just finishing up brewing up some fresh ground comments...