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From "Andrzej Bialecki (JIRA)" <>
Subject [jira] Created: (LUCENE-1420) Similarity.lengthNorm and positionIncrement=0
Date Mon, 13 Oct 2008 10:08:44 GMT
Similarity.lengthNorm and positionIncrement=0

                 Key: LUCENE-1420
             Project: Lucene - Java
          Issue Type: Improvement
          Components: Index
    Affects Versions: 2.3.3, 2.9
            Reporter: Andrzej Bialecki 
             Fix For: 2.3.3, 2.9

Calculation of lengthNorm factor should in some cases take into account the number of tokens
with positionIncrement=0. This should be made optional, to support two different scenarios:

* when analyzers insert artificially constructed tokens into TokenStream (e.g. ASCII-fied
versions of accented terms, stemmed terms), and it's unlikely that users submit queries containing
both versions of tokens: in this case lengthNorm calculation should ignore the tokens with

* when analyzers insert synonyms, and it's likely that users may submit queries that contain
multiple synonymous terms: in this case the lengthNorm should be calculated as it is now,
i.e. it should take into account all terms no matter what is their positionIncrement.

The default should be backward-compatible, i.e. it should count all tokens.

(See also the discussion here: )

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