Tim and I upgraded the lucene search engine during the weekend. It's currently up for en.wiki, rest is to come in next few days.
I already highlighted some of the features, but here's an update list:
* Improved scoring - the score of the document is now a function of how many other documents link to it. Same-namespace redirects now don't show up in the search results, their names are indexed alongside with the article they point to. E.g. searching USA will give you United States as first hit. Further, links from the beginning of the article are weighted more (as they are assumed to give a short keyword-like description of the article)
* Prefix searches - searcher now understands namespaces, i.e. if you enter help:images, it will search the Help namespace. You can also use the 'all' prefix that will search everything. Prefixes are customizable, i.e. you can make your custom prefixes (see below). I hope this will bring some ease in searching for help and searching the project/wikipedia namespace.
* Accentless search - accents are striped, this includes Hebrew pointing and similar, also adds common transliterations (eg ü -> ue)
* Numbers/stemming - numbers are now included in the index, and the stemming issues resolved...
If you want the install/customize the new search extension, take a look at: http://www.mediawiki.org/Extensions:LuceneSearch
Robert