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From "Mark Harwood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-329) Fuzzy query scoring issues
Date Mon, 15 Feb 2010 15:25:28 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-329?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12833840#action_12833840
] 

Mark Harwood commented on LUCENE-329:
-------------------------------------

My "best-practice" suggestion isn't as simple as offering a choice between preserving IDF
for all terms or not.

Instead, it is a proposal that we should use the *input* term's IDF for scoring all variants
of the same root term (or taking an average of variants where the root term does not exist).

This I feel preserves the benefits of keeping IDF as a factor (as in my John~ Patitucci~ balancing
example) but also eliminating the side effects we see where a rare mis-spelling beats exact
matches.


> Fuzzy query scoring issues
> --------------------------
>
>                 Key: LUCENE-329
>                 URL: https://issues.apache.org/jira/browse/LUCENE-329
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Search
>    Affects Versions: 1.2rc5
>         Environment: Operating System: All
> Platform: All
>            Reporter: Mark Harwood
>            Priority: Minor
>         Attachments: LUCENE-329.patch, patch.txt
>
>
> Queries which automatically produce multiple terms (wildcard, range, prefix, 
> fuzzy etc)currently suffer from two problems:
> 1) Scores for matching documents are significantly smaller than term queries 
> because of the volume of terms introduced (A match on query Foo~ is 0.1 
> whereas a match on query Foo is 1).
> 2) The rarer forms of expanded terms are favoured over those of more common 
> forms because of the IDF. When using Fuzzy queries for example, rare mis-
> spellings typically appear in results before the more common correct spellings.
> I will attach a patch that corrects the issues identified above by 
> 1) Overriding Similarity.coord to counteract the downplaying of scores 
> introduced by expanding terms.
> 2) Taking the IDF factor of the most common form of expanded terms as the 
> basis of scoring all other expanded terms.

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