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From "Mark Harwood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (LUCENE-644) Contrib: another highlighter approach
Date Wed, 02 Aug 2006 11:56:15 GMT
    [ http://issues.apache.org/jira/browse/LUCENE-644?page=comments#action_12425205 ] 
            
Mark Harwood commented on LUCENE-644:
-------------------------------------

I'm all for speed.

I'm just not sure I see why/where the optimization comes in over using existing Highlighter
+ TokenSources.getTokenStream

Can you post the client code that does the performance comparisons so I can see exactly what
it is you are comparing?


Thanks

> Contrib: another highlighter approach
> -------------------------------------
>
>                 Key: LUCENE-644
>                 URL: http://issues.apache.org/jira/browse/LUCENE-644
>             Project: Lucene - Java
>          Issue Type: Improvement
>          Components: Other
>            Reporter: Ronnie Kolehmainen
>            Priority: Minor
>         Attachments: FulltextHighlighter.java, FulltextHighlighterTest.java, svn-diff.patch
>
>
> Mark Harwoods highlighter package is a great contribution to Lucene, I've used it a lot!
However, when you have *large* documents (fields), highlighting can be quite time consuming
if you increase the number of bytes to analyze with setMaxDocBytesToAnalyze(int). The default
value of 50k is often too low for indexed PDFs etcetera, which results in empty highlight
strings.
> This is an alternative approach using term position vectors only to build fragment info
objects. Then a StringReader can read the relevant fragments and skip() between them. This
is a lot faster. Also, this method uses the *entire* field for finding the best fragments
so you're always guaranteed to get a highlight snippet.
> Because this method only works with fields which have term positions stored one can check
if this method works for a particular field using following code (taken from TokenSources.java):
>         TermFreqVector tfv = (TermFreqVector) reader.getTermFreqVector(docId, field);
>         if (tfv != null && tfv instanceof TermPositionVector)
>         {
>           // use FulltextHighlighter
>         }
>         else
>         {
>           // use standard Highlighter
>         }
> Someone else might find this useful so I'm posting the code here.

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