I have committed an unfinished and experimental, but basically working external search daemon and extension to use it, based on the Lucene search engine [1].
This enables searching to be moved out of MySQL and handled separately, thus not bogging down the database server with search queries and updates, as well as giving us the full power of a complete search engine, rather than MySQL's rather limited one. I suspect it will also be a bit faster; indexing en.wikibooks on a 1.1GHz Athlon with IDE disk takes 180 seconds (index size on disk: 53MB).
Other interesting possibilities include much shorter delays for search updates, incremental updates, various new ways to search other than title/body content, and so on.
To use it, check out the `lucene-search' module from CVS, and see the README.txt file for more information. Note that it ONLY works with 1.5. I may backport it to 1.4 at some future point.
Kate.