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From "thushara wijeratna (JIRA)" <j...@apache.org>
Subject [jira] Created: (LUCENE-2279) eliminate pathological performance on StopFilter when using a Set<String> instead of CharArraySet
Date Tue, 23 Feb 2010 00:35:30 GMT
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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