Search on RationalWiki uses Lucene. The Lucene index hadn't actually updated since July 2012 - because incremental updating didn't work, because Trent had to disable the OAIRepository extension because it was breaking other stuff.
A complete reindex (we're currently around 86,000 pages total) takes 20-30 minutes, so David's set it to run one of those weekly. This is not ideal, but is a vast improvement.
Fixing it properly will require fixing OAIRepository, and possibly even writing documentation that doesn't have a big red warning saying it's completely wrong. Anyone feeling inspired?