A Similarity class which extends DefaultSimilarity and simply overrides lengthNorm. lengthNorm is implemented as a lookup for numTerms <= 10, else as 1/sqrt(numTerms). This is to avoid term counts below 11 from having the same lengthNorm after stored as a single byte in the index.
This is useful if your search is only on short fields such as titles or product descriptions.
See mailing list discussion: http://www.nabble.com/How-to-boost-the-score-higher-in-case-user-query-matches-entire-field-value-than-just-some-words-within-a-field-td19079221.html