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List:       lucene-dev
Subject:    [jira] Commented: (LUCENE-446) FunctionQuery - score based on field value
From:       "Yonik Seeley (JIRA)" <jira () apache ! org>
Date:       2005-11-30 18:16:30
Message-ID: 34114203.1133374590105.JavaMail.jira () ajax ! apache ! org
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    [ http://issues.apache.org/jira/browse/LUCENE-446?page=comments#action_12358936 ] \


Yonik Seeley commented on LUCENE-446:
-------------------------------------

This newest version simplifies a lot of cruft from the previous version.

A FunctionQuery takes a ValueSource.
The ValueSource produces a DocValues object for a specific IndexReader (It's like a \
lucene scorer). The ValueSource is also used as input to functions, which are \
ValueSources themselves.

So, you can do things (symbolically), like

int(fieldx)
float(fieldx)
ord(fieldx)
rord(fieldx)
linear(fieldx,1,2)
linear(rord(fieldx),1,2,3)
reciprocal(linear(fieldx,1,2),3,4,5)

A useful one for boosting more recent dates might be:
reciprocal(rord(mydatefield),1,1000,1000)

I'm not sure if this is the final form yet... perhaps the division between \
ValueSource and Query  could be erased such that every value source is a query \
already (so that you don't need to pass it to a FunctionQuery).

It would also be nice to freely mix a lucene Query and a ValueSource so that you \
could do something like: product(luceneQuery, val(fieldx))
  or even
product(luceneQuery1, luceneQuery2)

Of course, I haven't done the "product" function yet... right now, the normal way \
tocombine with other queries to influence the score is to put it in a boolean query: \
+other_lucene_query_clauses +function_query^.1 the score from the function query is \
added to the other query.


> FunctionQuery - score based on field value
> ------------------------------------------
> 
> Key: LUCENE-446
> URL: http://issues.apache.org/jira/browse/LUCENE-446
> Project: Lucene - Java
> Type: New Feature
> Components: Search
> Versions: 1.9
> Reporter: Yonik Seeley
> Attachments: function.zip
> 
> FunctionQuery can return a score based on a field's value or on it's ordinal value.
> FunctionFactory subclasses define the details of the function.  There is currently \
> a LinearFloatFunction (a line specified by slope and intercept). Field values are \
> typically obtained from FieldValueSourceFactory.  Implementations include \
> FloatFieldSource, IntFieldSource, and OrdFieldSource.

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