How should i implement "2-way" text indexing on Google App Engine?

I want to implement both active search, where keyword queries matches text content, and passive se开发者_如何学运维arch, where new content matches stored queries, on my google app engine application.

I have never implemented indexing and searching algorithms, could you throw me some starting points?

For active search this is a good starting point: http://www.billkatz.com/2009/6/Simple-Full-Text-Search-for-App-Engine

It has some limitations, but the code is pretty simple to expand. In my app I added better unicode support, as well as prefix-matching so that autocompletion would work as a user types in a search term.

For passive search, depends on the use case, it seems like it could be taken care of with task queues to check an entity against many queries, or having queries running on a cron job to check for new matches continuously.