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Highlighting span for Phrase Queries

Subject: Highlighting span for Phrase Queries
From: Heikki Doeleman
Date: Fri, 10 Nov 2006 15:45:23 +0100
Hi there,

I have a question on using the Highlighter.

I'm using Lucene in a web application that allows you to search the 
catalogue of a library. The idea is to highlight, in the results, the 
terms entered by the user. I'm using a Highlighter with a NullFragmenter 
because I want the whole field highlighted (for each field the user 
searched in).

The catalogue is indexed with a StandardAnalyzer on each field. 
Highlighting a field from a result I do like this  :

            QueryScorer scorer = new QueryScorer ( theQuery, 
searcher.getIndexReader ( ) , fieldName ) ;
            Highlighter highlighter = new Highlighter ( new 
SimpleHTMLFormatter ( "<span style=\"border-style:solid;\">" , "</span>" ) 
, scorer ) ;
            highlighter. setTextFragmenter ( new NullFragmenter ( ) ) ;

        highlightedFieldContent = highlighter. getBestFragment ( analyzer 
, fieldName , originalFieldContent ) ; 

This works all very well, except for phrase queries. The spans of the 
phrase queries as such are not highlighted and instead, each of the terms 
that is in the phrase query, gets highlighted. I guess this is because the 
indexed fields have been tokenized, and what-not, by the StandardAnalyzer.

Does anyone have a good example about how to implement a highlighting 
function that works well with phrase queries, too ?

thank you very much.

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