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