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From "Andrzej Bialecki (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-1420) Similarity.lengthNorm and positionIncrement=0
Date Sat, 25 Oct 2008 22:56:44 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-1420?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Andrzej Bialecki  updated LUCENE-1420:
--------------------------------------

    Attachment: similarity-v2.patch

Patch that uses FieldInvertState, as suggested. Changes in other classes are limited to minimum
in this patch - users of Similarity other than o.a.l.index.* still use lengthNorm(String,
int).

> Similarity.lengthNorm and positionIncrement=0
> ---------------------------------------------
>
>                 Key: LUCENE-1420
>                 URL: https://issues.apache.org/jira/browse/LUCENE-1420
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Index
>    Affects Versions: 2.3.3, 2.9
>            Reporter: Andrzej Bialecki 
>            Assignee: Michael McCandless
>             Fix For: 2.3.3, 2.9
>
>         Attachments: similarity-v2.patch, similarity.patch
>
>
> 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
positionIncrement=0.
> * 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: http://markmail.org/message/vfvmzrzhr6pya22h )

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