The search capability on Wikipedia was modified by the developers last week as they work to improve performance and the quality of results.
On Monday, Chief Technical Officer Brion Vibber announced that he had changed the way the searching function works. In conjunction with MediaWiki software, Wikipedia uses a full-text search based on a Lucene core.
The change made affects searches that include more than one term, as results will now only show matches that contain all terms given. As Vibber explained, "This gives more focused results and is more consistent with typical search engine practice, and our behavior under the old MySQL search." In order to make a term optional, one should now use an OR operator (which must be capitalized). The use of Boolean logic remains available to construct searches generally.
The developers also responded to a complaint from Phil Boswell that the search function was producing errors. Tim Starling explained that the servers were occasionally hanging, necessitating periodic restarts of the daemons. Errors can also result from heavy server loads.
The search function is now supported by three servers, and configured to try the other two if one doesn't respond. This will hopefully reduce the amount of time for which internal searching is unavailable. For situations in which all three servers fail, a form showing the Google and Yahoo search options will remain in place.