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From Jack Krupansky <>
Subject Re: Calculate the score of an arbitrary string vs a query?
Date Fri, 10 Apr 2015 21:32:44 GMT
There is doc for tf*idf scoring in the javadoc:

The IndexSearcher#explain method returns an Explanation structure which
details the scoring for a document:,

-- Jack Krupansky

On Fri, Apr 10, 2015 at 4:15 PM, Gregory Dearing <>

> Hi Ali,
> The short answer to your question is... there's no good way to create a
> score from your result string, without using the Lucene index, that will be
> directly comparable to the Lucene score.  The reason is that the score
> isn't just a function of the query and the contents of the document.  It's
> also (usually) a function of the contents of the entire corpus... or rather
> how common terms are across the entire corpus.
> That being said... the default scoring algorithm is based on tf/idf.  The
> implementation isn't in any one class... every query type (e.g. Term Query,
> Boolean Query, etc...) contains its own code for calculating scores.  So
> the complete scoring formula will depend on the type of queries you're
> using.  Many of those implementations also call into the Similarity API
> that you mentioned.
> If you'd like to see representative examples of scoring code, then take a
> look at TermWeight/TermScorer, and also BooleanWeight, which has several
> associated scorers.
> -Greg
> On Tue, Apr 7, 2015 at 1:32 AM, Ali Akhtar <> wrote:
> > Hello,
> >
> > I'm in a situation where a search query string is being submitted
> > simultaneously to Lucene, and to an external API.
> >
> > Results are fetched from both sources. I already have a score available
> for
> > Lucene results, but I don't have a score for the results fetched from the
> > external source.
> >
> > I'd like to calculate scores of results from the API, so that I can rank
> > the results by the score, and show the top 5 results from both sources.
> > (I.e the results would be merged.)
> >
> > Is there any Lucene API method, to which I can submit a search string and
> > result string, and get a score back? If not, which class contains the
> > source code for calculating the score, so that I can implement my own
> > scoring class, using the same algorithm?
> >
> > I've looked at the Similarity class Javadocs, but it doesn't include any
> > source code for calculating the score.
> >
> > Any help would be greatly appreciated. Thanks.
> >

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