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From "thushara wijeratna (JIRA)" <j...@apache.org>
Subject [jira] Updated: (LUCENE-2279) eliminate pathological performance on StopFilter when using a Set<String> instead of CharArraySet
Date Tue, 23 Feb 2010 00:39:30 GMT

     [ https://issues.apache.org/jira/browse/LUCENE-2279?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

thushara wijeratna updated LUCENE-2279:
---------------------------------------


a yourkit profile (before/after):

http://thushw.blogspot.com/2010/02/interesting-performance-characteristic.html

> eliminate pathological performance on StopFilter when using a Set<String> instead
of CharArraySet
> -------------------------------------------------------------------------------------------------
>
>                 Key: LUCENE-2279
>                 URL: https://issues.apache.org/jira/browse/LUCENE-2279
>             Project: Lucene - Java
>          Issue Type: Improvement
>            Reporter: thushara wijeratna
>
> passing a Set<Srtring> to a StopFilter instead of a CharArraySet results in a very
slow filter.
> this is because for each document, Analyzer.tokenStream() is called, which ends up calling
the StopFilter (if used). And if a regular Set<String> is used in the StopFilter all
the elements of the set are copied to a CharArraySet, as we can see in it's ctor:
> public StopFilter(boolean enablePositionIncrements, TokenStream input, Set stopWords,
boolean ignoreCase)
>   {
>     super(input);
>     if (stopWords instanceof CharArraySet) {
>       this.stopWords = (CharArraySet)stopWords;
>     } else {
>       this.stopWords = new CharArraySet(stopWords.size(), ignoreCase);
>       this.stopWords.addAll(stopWords);
>     }
>     this.enablePositionIncrements = enablePositionIncrements;
>     init();
>   }
> i feel we should make the StopFilter signature specific, as in specifying CharArraySet
vs Set, and there should be a JavaDoc warning on using the other variants of the StopFilter
as they all result in a copy for each invocation of Analyzer.tokenStream().

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