Implement a state-of-the-art retrieval function in Lucene
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Key: LUCENE-965
URL: https://issues.apache.org/jira/browse/LUCENE-965
Project: Lucene - Java
Issue Type: Improvement
Components: Search
Affects Versions: 2.2
Reporter: Hui Fang
We implemented the axiomatic retrieval function, which is a state-of-the-art
retrieval function, to
replace the default similarity function in Lucene. We compared the performance
of these two functions and reported the results at
http://sifaka.cs.uiuc.edu/hfang/lucene/Lucene_exp.pdf.
The report shows that the performance of the axiomatic retrieval function is
much better than the default function. The axiomatic retrieval function is able
to find more relevant documents and users can see more relevant documents in
the top-ranked documents. Incorporating such a state-of-the-art retrieval
function could improve the search performance of all the applications which
were built upon Lucene.
Most changes related to the implementation are made in AXSimilarity, TermScorer
and TermQuery.java. However, many test cases are hand coded to test whether
the implementation of the default function is correct. Thus, I also made the
modification to many test files to make the new retrieval function pass those
cases. In fact, we found that some old test cases are not reasonable. For
example, in the testQueries02 of TestBoolean2.java,
the query is "+w3 xx", and we have two documents "w1 xx w2 yy w3" and "w1 w3 xx
w2 yy w3".
The second document should be more relevant than the first one, because it has
more
occurrences of the query term "w3". But the original test case would require us
to rank
the first document higher than the second one, which is not reasonable.
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