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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-2286) enable DefaultSimilarity.setDiscountOverlaps by default
Date Thu, 25 Feb 2010 14:25:27 GMT
enable DefaultSimilarity.setDiscountOverlaps by default
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                 Key: LUCENE-2286
                 URL: https://issues.apache.org/jira/browse/LUCENE-2286
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Query/Scoring
            Reporter: Robert Muir


I think we should enable setDiscountOverlaps in DefaultSimilarity by default.

If you are using synonyms or commongrams or a number of other 0-posInc-term-injecting methods,
these currently screw up your length normalization.
These terms have a position increment of zero, so they shouldnt count towards the length of
the document.

I've done relevance tests with persian showing the difference is significant, and i think
its a big trap to anyone using synonyms, etc: your relevance can actually get worse if you
don't flip this boolean flag.

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