One reason it is probably not as fast as we'd like, is the way to builds the search results display.
The search package currently re-queries the datasource procedure for each displayed result (10 on a page) which means 10 or more queries to display one page of results.
I suspect bugtracker is pretty complex to get the full datasource.
The next generation search engine caches the datasource in a table so headline data can be retrieved with the search results.
The work for that is on HEAD and is working for Oracle, it needs some work on PostgreSQL still.
