Brion Vibber said:
Our currently-live search does basic stemming for English, German, Russian, and Esperanto, but not for other languages.
The issue Robert mentioned was that the old way would return results with any inflected form unconditionally, which can be annoying when you really did want an exact match. The new code has a preference for exact matches in the ranking, but will return related inflected forms as well.
I guess Wikipedia is using SnowballAnalyzer rather than StandardAnalyzer? To my knowledge, the later one does not using any stemmer.
Regards, /Mike "b6s" Jiang/