Explain shows incorrect docFreq number when used for documents in different
indices searched via MultiSearcher
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Key: LUCENE-1087
URL: https://issues.apache.org/jira/browse/LUCENE-1087
Project: Lucene - Java
Issue Type: Bug
Components: Query/Scoring
Affects Versions: 2.2
Environment: No special hardware required to reproduce the issue.
Reporter: Yasoja Seneviratne
Priority: Minor
Creating 2 different indexes, searching each individually and print score
details and compare to searching both indexes with MulitSearcher and printing
score details.
The "docFreq" value printed isn't correct - the values it prints are as if each
index was searched individually.
Code is like:
MultiSearcher multi = new MultiSearcher(searchables);
Hits hits = multi.search(query);
for(int i=0; i<hits.length(); i++)
{
Explanation expl = multi.explain(query, hits.id(i));
System.out.println(expl.toString());
}
I raised this in the Lucene user mailing list and was advised to log a bug,
email thread given below.
-----Original Message-----
From: Chris Hostetter [mailto:[EMAIL PROTECTED]
Sent: Friday, December 07, 2007 10:30 PM
To: [EMAIL PROTECTED]
Subject: Re: does the MultiSearcher class calculate IDF properly?
a quick glance at the code seems to indicate that MultiSearcher has code
for calcuating the docFreq accross all of the Searchables when searching
(or when the docFreq method is explicitly called) but that explain method
just delegates to Searchable that the specific docid came from.
if you compare that Explanation score you got with the score returned by
a HitCollector (or TopDocs) they probably won't match.
So i would say "yes MultiSearcher calculates IDF properly, but
MultiSeracher.explain is broken. Please file a bug about this, i can't
think of an easy way to fix it, but it certianly seems broken to me.
: Subject: does the MultiSearcher class calculate IDF properly?
:
: I tried the following. Creating 2 different indexes, search each
: individually and print score details and compare to searching both
: indexes with MulitSearcher and printing score details.
:
: The "docFreq" value printed don't seem right - is this just a problem
: with using Explain together with the MultiSearcher?
:
:
: Code is like:
: MultiSearcher multi = new MultiSearcher(searchables);
: Hits hits = multi.search(query);
: for(int i=0; i<hits.length(); i++)
: {
: Explanation expl = multi.explain(query, hits.id(i));
: System.out.println(expl.toString());
: }
:
:
: Output:
: id = 14 score = 0.071
: 0.07073946 = (MATCH) fieldWeight(contents:climate in 2), product of:
: 1.0 = tf(termFreq(contents:climate)=1)
: 1.8109303 = idf(docFreq=1)
: 0.0390625 = fieldNorm(field=contents, doc=2)
:
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:
-Hoss
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