To update with some more recent info (2013), GAE now has a text search API. You can't search data in the database directly; you create searchable documents from your data, and add those to a searchable index. It's not terribly hard to do, but it's a hassle. In particular, whenever your data changes, you need to re-regenerate the changed documents and update them in the index.
It's also fairly easy to export data into Google Big Query, which makes it easy to do reporting.
