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From "Eks Dev (JIRA)" <>
Subject [jira] Commented: (LUCENE-329) Fuzzy query scoring issues
Date Mon, 15 Feb 2010 15:55:28 GMT


Eks Dev commented on LUCENE-329:

query for John~ Patitucci~ I'm probably more interested in a partial match on the rarer surname
than a partial match on the common forename. 

as a matter of fact, we have not only one frequency  to consider, rather two Term frequencies!

consider simpler case
Query term: "Johan" //would be High frequency term
Fuzzy Expanded term1 "Johana" // High frequency
Fuzzy Expanded term2 "Joahn" // Low Freq

I guess you would like to score the second term higher, meaning Lower frequency (higher IDF)...
So far so good. 

Now turn it upside down and search for LF typo "Joahn"... in that case you would preffer HF
Term "Johan" from expanded list to score higher...

Point being, this situation here is just not "complete" without taking both frequencies into
consideration (Query Term and Expanded term). In my experience, some simple nonlinear hints
based on these two freqs bring some easy precision points (HF-LF Pairs are much more likely
to be typos that two HF-HF...  ). 

> Fuzzy query scoring issues
> --------------------------
>                 Key: LUCENE-329
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: Search
>    Affects Versions: 1.2rc5
>         Environment: Operating System: All
> Platform: All
>            Reporter: Mark Harwood
>            Priority: Minor
>         Attachments: 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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