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From "Robert Muir (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (LUCENE-4825) PostingsHighlighter support for positional queries
Date Wed, 13 Mar 2013 10:46:12 GMT

    [ https://issues.apache.org/jira/browse/LUCENE-4825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13601017#comment-13601017
] 

Robert Muir commented on LUCENE-4825:
-------------------------------------

I dont see this highlighter as doing that I guess.

I see it as taking query *terms* (not matches!!!!) and intersecting them with a breakiterator
in increasing offset order, ranking these passages as it goes.

{quote}
We would need to read the spans from the positional queries in order to highlight only the
proper terms, otherwise the output is wrong from a user perspective.
{quote}

Then the user is wrong, and should use another highlighter. This one is about good document
summarization with respect to the query terms. Its not about visualizing exact matches to
lucene queries.

If the user doesnt care about 'search' but about 'matching' at the expense of everything else,
they already have 2 other highlighters in lucene that focus on this (making wrong tradeoffs
in my opinion)!

                
> PostingsHighlighter support for positional queries
> --------------------------------------------------
>
>                 Key: LUCENE-4825
>                 URL: https://issues.apache.org/jira/browse/LUCENE-4825
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/highlighter
>    Affects Versions: 4.2
>            Reporter: Luca Cavanna
>
> I've been playing around with the brand new PostingsHighlighter. I'm really happy with
the result in terms of quality of the snippets and performance.
> On the other hand, I noticed it doesn't support positional queries. If you make a span
query, for example, all the single terms will be highlighted, even though they haven't contributed
to the match. That reminds me of the difference between the QueryTermScorer and the QueryScorer
(using the standard Highlighter).
> I've been trying to adapt what the QueryScorer does, especially the extraction of the
query terms together with their positions (what WeightedSpanTermExtractor does). Next step
would be to take that information into account within the formatter and highlight only the
terms that actually contributed to the match. I'm not quite ready yet with a patch to contribute
this back, but I certainly intend to do so. That's why I opened the issue and in the meantime
I would like to hear what you guys think about it and  discuss how best we can fix it. I think
it would be a big improvement for this new highlighter, which is already great!

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