Jim Hu wrote:
As I understand it, Lucene indexes and stores the indexes into a set of index files that are kept in memory or are swapped in as needed and does not use the backend database that's running the wiki. By contrast, Sphinx works via mySQL.
Regarding indexes, Sphinx can be set up to use either a MySQL backend or it's own data format, which is the standard mode. It might be though that the SphinxSearch extension ( http://www.mediawiki.org/wiki/Extension:SphinxSearch ) uses the wiki's database to get the article extracts for the search page, since these extracts are not in the indexes.
I have, btw, been impressed by Sphinx's indexing speed (something like 1000 pages / 6 sec) , as well as it's set of features and config options (mutli-language stemming et.c.), and think it looks very promising.
Regards Samuel