On Thu, Mar 3, 2011 at 10:25 AM, Patrick Diviacco <patrick.divia...@gmail.com> wrote: > I've downloaded Lucene nightly build because I need to customize the > similarity *per field*. > > However I don't see the field parameter passed to the methods to compute the > score such as "tf" and "idf"... > > how can I implement different similarities score per document field then ? >
Hi, the way you set this up is to use SimilarityProvider to configure Similarities per-field: for example maybe field A, B, and C use Similarity1 and field D use Similarity2. So you just set your SimilarityProvider on the IndexWriter and IndexSearcher, and it must implement this factory method: Similarity get(String field) Here are the reasons for this factory design (versus simply adding field to every method): 1. performance: up-front we ask the SimilarityProvider for the per-field Similarity. So you probably use a hashmap or something here to return the correct one. If you had to do this on every single call to tf(), this would slow down queries significantly. 2. flexibility: we are working to generalize Similarity, and maybe the existing stuff you see becomes TFIDFSimilarity. So in the future you might have field1 that uses TFIDF and field2 that uses something else (e.g. BM25), with a totally different API and scoring system. --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
