For our intranet's collection of tens of thousands of pages, results come back in a fraction of a second. Accuracy seems as good as the ten-year-old Google Mini Search Appliance that it replaced, but I had to write a good chunk of SQL. I weigh whether the terms are in the web address, title, or just the body, and also the number of backlinks. This took making a few tables, views, and SQL functions, as well as a daily cron job.