Hi, You don't need to extend BooleanQuery, you can just pass "true" in its ctor, see: http://s.apache.org/QvK Of course you can also subclass DefaultSimilarity and return 1 as coord, but that is more work than passing true to a ctor.
For your type of queries, disabling coord should be enough, but I am not 100% sure! Why not simply try it out? Uwe ----- Uwe Schindler H.-H.-Meier-Allee 63, D-28213 Bremen http://www.thetaphi.de eMail: u...@thetaphi.de > -----Original Message----- > From: Patrick Diviacco [mailto:patrick.divia...@gmail.com] > Sent: Monday, March 28, 2011 10:49 AM > To: java-user@lucene.apache.org > Subject: Re: comparing lucene scores across queries > > One more thing, instead of extending the BooleanQuery class to remove the > coord factor, can I also extend the Similarity class to do it ? > > Still the other question is open: just to be sure, if I disable the coord factor I > can finally compare my BooleanQuery results ? > > thanks > > > > > > > > > On 28 March 2011 10:11, Uwe Schindler <u...@thetaphi.de> wrote: > > > >> Hi Patrick, > >> > >> You can disable the coord factor in the constructor of BooleanQuery. > >> > >> Uwe > >> > >> ----- > >> Uwe Schindler > >> H.-H.-Meier-Allee 63, D-28213 Bremen > >> http://www.thetaphi.de > >> eMail: u...@thetaphi.de > >> > >> > >> > -----Original Message----- > >> > From: Patrick Diviacco [mailto:patrick.divia...@gmail.com] > >> > Sent: Monday, March 28, 2011 10:09 AM > >> > To: java-user@lucene.apache.org > >> > Subject: Re: comparing lucene scores across queries > >> > > >> > Hi, thanks for reply. > >> > > >> > Yeah, I've read the Similarity class documentation several times, > >> > but I > >> need > >> > some tip. > >> > > >> > My queries are BooleanQueries but they always have the same > >> > structure (the same structure of the docs, they are actually docs > >> > from > >> collection): > >> 3 > >> > fields. > >> > > >> > What if I simplify the similarity scores, by removing coord factor > >> > and > >> just > >> > leaving the cosine similarity which is comparable ? > >> > > >> > I want to underline the fact that my boolean queries are just a > >> combination > >> > of "field:term" items, and I always have the same 3 fields with > >> different > >> > terms obviously. > >> > > >> > Thanks > >> > > >> > > >> > > >> > > >> > On 28 March 2011 10:03, Uwe Schindler <u...@thetaphi.de> wrote: > >> > > >> > > No, scores are in general not comparable between different queries. > >> > > The problem lies in many things: > >> > > - Each query has a norm factor that makes it more compareable if > >> > > they are sub clauses of a BooleanQuery. But you are right, this > >> > > norm factor should be the same. > >> > > - Some queries like FuzzyQuery rely on the terms in index and > >> > > those matches the query > >> > > - Inside Boolean queries, there is also a coord-factor involved > >> > > > >> > > If you are always using the same simple type of query (e.g. > >> > > simple TermQuery, only with different term) on the same index, > >> > > you can compare the scores. As soon as you are using complex > >> > > queries (e.g several terms compared in a BooleanQuery as > >> > > QueryParser produces), the scores are no longer comparable. > >> > > > >> > > You can read more on all factors that are included in scoring: > >> > > > >> > > > >> > > http://lucene.apache.org/java/3_0_3/api/core/org/apache/lucene/sear > >> > ch/ > >> > > Simila > >> > > rity.html > >> > > > >> > > ----- > >> > > Uwe Schindler > >> > > H.-H.-Meier-Allee 63, D-28213 Bremen http://www.thetaphi.de > >> > > eMail: u...@thetaphi.de > >> > > > >> > > > >> > > > -----Original Message----- > >> > > > From: Patrick Diviacco [mailto:patrick.divia...@gmail.com] > >> > > > Sent: Monday, March 28, 2011 9:44 AM > >> > > > To: java-user@lucene.apache.org > >> > > > Subject: comparing lucene scores across queries > >> > > > > >> > > > Hi, > >> > > > > >> > > > sorry I've already asked few days ago, but I got no reply and I > >> > > > really > >> > > need > >> > > > some help on this.. > >> > > > > >> > > > I'm running several queries against a doc collection. The queries > >> > > > are documents of the collection itself, I need to measure how > >> > > > similar is each document to the rest of the collection. > >> > > > > >> > > > Now, Lucene returns me a score per query, but I've been told such > >> > > > score > >> > > is > >> > > > not comparable across queries. Is this correct ? > >> > > > > >> > > > For example, arem't these scores comparable ? > >> > > > query1, score:8.324234 > >> > > > query2, score:3.324238 > >> > > > > >> > > > If so, why not ? Isn't the cosine similarity between the query > >> > > > vector and collection docs vectors ? I really need a comparable > >> measure. > >> > > > > >> > > > thanks > >> > > > >> > > > >> > > --------------------------------------------------------------------- > >> > > To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > >> > > For additional commands, e-mail: java-user-h...@lucene.apache.org > >> > > > >> > > > >> > >> > >> --------------------------------------------------------------------- > >> To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org > >> For additional commands, e-mail: java-user-h...@lucene.apache.org > >> > >> > > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
