EnglishPorterFilterFactory
Thats the short answer ;)
A little more information:
English Porter means the english porter stemmer stemming alogrithm. And both elegant and elegance have according to the stemmer (which is a heuristical word root builder) the same stem.
You can verify this online e.g. Here. Basically you will see "eleg ant " and "eleg ance" stemmed to the same stem > eleg.
From Solr source:
public void inform(ResourceLoader loader) {
String wordFiles = args.get(PROTECTED_TOKENS);
if (wordFiles != null) {
try {
Here exactly comes the protwords file into play:
File protectedWordFiles = new File(wordFiles);
if (protectedWordFiles.exists()) {
List<String> wlist = loader.getLines(wordFiles);
//This cast is safe in Lucene
protectedWords = new CharArraySet(wlist, false);//No need to go through StopFilter as before, since it just uses a List internally
} else {
List<String> files = StrUtils
.splitFileNames(wordFiles);
for (String file : files) {
List<String> wlist = loader.getLines(file
.trim());
if (protectedWords == null)
protectedWords = new CharArraySet(wlist,
false);
else
protectedWords.addAll(wlist);
}
}
} catch (IOException e) {
throw new RuntimeException(e);
}
}
}
Thats the part which affects the stemming. There you see the invocation of the snowball library
public EnglishPorterFilter create(TokenStream input) {
return new EnglishPorterFilter(input, protectedWords);
}
}
/**
* English Porter2 filter that doesn't use reflection to
* adapt lucene to the snowball stemmer code.
*/
@Deprecated
class EnglishPorterFilter extends SnowballPorterFilter {
public EnglishPorterFilter(TokenStream source,
CharArraySet protWords) {
super (source, new org.tartarus.snowball.ext.EnglishStemmer(),
protWords);
}
}
