Wikipedia, and particularly the related sites running the software as MediaWiki, have some of the worst site search I have ever seen. The default installation's query processing is absurdly limited, the retrieval is crippled by bad settings, the relevance is unclear, and the results page is not just ugly but contradictory and confusing.
I will be posting more detailed analyses supporting each of these statements, linked from this blog.
Default versions of the wikimedia search engine are very nearly unusable. If you have a MediaWiki, check the page Special:Version. If there is no mention of a search plugin, then run, do not walk, to replace the site search module. At least use the MWSearch (Lucene) extension, a version of which is used on the main wikipedia, or, better, the Sphinx search extension (which powers the New World Encyclopedia search). Your wiki readers will thank you.
What MediaWiki Default Search Does Wrong
more to come.
There are also some things that the MediaWiki search does right, but mostly, I've found it just stinks.
Arguments? Questions? Comments? I'm interested in other people's experiences, and may be able to deconstruct problems with the search.