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Date: Fri, 10 Feb 2006 09:41:57 +0100 (CET)
From: "Hoss Man (JIRA)" <jira@apache.org>
To: java-dev@lucene.apache.org
Subject: [jira] Commented: (LUCENE-323) [PATCH] MultiFieldQueryParser and
 BooleanQuery do not provide adequate support for queries across multiple
 fields
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    [ http://issues.apache.org/jira/browse/LUCENE-323?page=comments#action_12365858 ] 

Hoss Man commented on LUCENE-323:
---------------------------------

The WIkipediaSimilarity seems to only have been included as an example for the purposes of comparison testing, not as an item to be commited.

Given Chuck's comment on 21/Dec/05 I'm of the opinion this issue should be closed.

> [PATCH] MultiFieldQueryParser and BooleanQuery do not provide adequate support for queries across multiple fields
> -----------------------------------------------------------------------------------------------------------------
>
>          Key: LUCENE-323
>          URL: http://issues.apache.org/jira/browse/LUCENE-323
>      Project: Lucene - Java
>         Type: Bug
>   Components: QueryParser
>     Versions: 1.4
>  Environment: Operating System: Windows XP
> Platform: PC
>     Reporter: Chuck Williams
>     Assignee: Lucene Developers
>  Attachments: DisjunctionMaxQuery.java, DisjunctionMaxScorer.java, TestDisjunctionMaxQuery.java, TestMaxDisjunctionQuery.java, TestRanking.zip, TestRanking.zip, TestRanking.zip, WikipediaSimilarity.java, WikipediaSimilarity.java, WikipediaSimilarity.java, dms.tar.gz
>
> The attached test case demonstrates this problem and provides a fix:
>   1.  Use a custom similarity to eliminate all tf and idf effects, just to 
> isolate what is being tested.
>   2.  Create two documents doc1 and doc2, each with two fields title and 
> description.  doc1 has "elephant" in title and "elephant" in description.  
> doc2 has "elephant" in title and "albino" in description.
>   3.  Express query for "albino elephant" against both fields.
> Problems:
>       a.  MultiFieldQueryParser won't recognize either document as containing 
> both terms, due to the way it expands the query across fields.
>       b.  Expressing query as "title:albino description:albino title:elephant 
> description:elephant" will score both documents equivalently, since each 
> matches two query terms.
>   4.  Comparison to MaxDisjunctionQuery and my method for expanding queries 
> across fields.  Using notation that () represents a BooleanQuery and ( | ) 
> represents a MaxDisjunctionQuery, "albino elephant" expands to:
>         ( (title:albino | description:albino)
>           (title:elephant | description:elephant) )
> This will recognize that doc2 has both terms matched while doc1 only has 1 
> term matched, score doc2 over doc1.
> Refinement note:  the actual expansion for "albino query" that I use is:
>         ( (title:albino | description:albino)~0.1
>           (title:elephant | description:elephant)~0.1 )
> This causes the score of each MaxDisjunctionQuery to be the score of highest 
> scoring MDQ subclause plus 0.1 times the sum of the scores of the other MDQ 
> subclauses.  Thus, doc1 gets some credit for also having "elephant" in the 
> description but only 1/10 as much as doc2 gets for covering another query term 
> in its description.  If doc3 has "elephant" in title and both "albino" 
> and "elephant" in the description, then with the actual refined expansion, it 
> gets the highest score of all (whereas with pure max, without the 0.1, it 
> would get the same score as doc2).
> In real apps, tf's and idf's also come into play of course, but can affect 
> these either way (i.e., mitigate this fundamental problem or exacerbate it).

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