[jira] Commented: (LUCENE-446) FunctionQuery - score based on field value

["Kelvin Tan (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/LUCENE-446?page=comments#action_12366302 ] 

Kelvin Tan commented on LUCENE-446:
-----------------------------------

Yes, I've independently come up with something similar. What's interesting is that you can also perform filtering (like date filtering) by simply returning negative Float.MAX_VALUE. This pretty much guarantees that the document's final score is < 0.

I've also come across the need to be able to modify the final score of a document, and have done this via a score-modifying query wrapper which delegates the scoring to the functionquery it wraps, then applying an additional function to it. Is that similar to the product function you mention?

> 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, 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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