[jira] Commented: (NUTCH-134) Summarizer doesn't select the best snippets

["Doug Cutting (JIRA)" <ji...@apache.org>]

    [ http://issues.apache.org/jira/browse/NUTCH-134?page=comments#action_12359626 ] 

Doug Cutting commented on NUTCH-134:
------------------------------------

Can we yet replace Nutch's summarizer with the summarizer in Lucene's contrib directory?  Are there features that Nutch requires that that does not yet implement?  It's a shame to maintain two summarizers.  When I first wrote Nutch's summarizer there was no Lucene contrib summarizer...

> Summarizer doesn't select the best snippets
> -------------------------------------------
>
>          Key: NUTCH-134
>          URL: http://issues.apache.org/jira/browse/NUTCH-134
>      Project: Nutch
>         Type: Bug
>   Components: searcher
>     Versions: 0.7, 0.8-dev, 0.7.1, 0.7.2-dev
>     Reporter: Andrzej Bialecki 

>
> Summarizer.java tries to select the best fragments from the input text, where the frequency of query terms is the highest. However, the logic in line 223 is flawed in that the excerptSet.add() operation will add new excerpts only if they are not already present - the test is performed using the Comparator that compares only the numUniqueTokens. This means that if there are two or more excerpts, which score equally high, only the first of them will be retained, and the rest of equally-scoring excerpts will be discarded, in favor of other excerpts (possibly lower scoring).
> To fix this the Set should be replaced with a List + a sort operation. To keep the relative position of excerpts in the original order the Excerpt class should be extended with an "int order" field, and the collected excerpts should be sorted in that order prior to adding them to the summary.

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