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From Dmitry Serebrennikov <>
Subject Re: Document Scoring
Date Thu, 04 Apr 2002 20:03:01 GMT
>Now, the class IndexSearcher, which extends Searcher, refers back to  the IndexReader.
Here is the puzzling part:
>    The method docFreq(Term t) and the method maxDoc() are both declared abstract in IndexReader.
>Faced with this question, I was obliged to check out how it was done in the demo that
comes with Lucene. But the demo still uses IndexSearcher which in turn uses IndexReader to
call these methods.
There are a couple of kinds of IndexReaders that are supported. One is 
called SegmentReader and the other - SegmentsReader (notice the ploral). 
The first one is used to access a single index segment, whereas the 
second one is used to do a search in unoptimized indexes that have more 
then one segment. These are implementation classes that extend 
IndexReader in different ways. Other readers could potentially be 
created as well that would use implement access into some other kind of 
a datastructure.

Not sure if this sheds any light onto your original question about how 
the scoring works, but it should explaing the mystery of the abstract 
methods. As far as the scoring, you will probably find your questions 
answered by one of the FAQs. They give the answer in terms of the 
searching theory that might save you time in trying to figure this out 
from code. I would include the answer here, but I'm not that strong in 
the theory/math of it, so the FAQ is your best bet. I just know it 
works, and that happens to be good enough for me today :).


>Can anyone please shed some light here?

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