Question

when i query for “elegant” in solr i get results for “elegance” too.

I used these filters for index analyze

WhitespaceTokenizerFactory
StopFilterFactory
WordDelimiterFilterFactory
LowerCaseFilterFactory
SynonymFilterFactory
EnglishPorterFilterFactory
RemoveDuplicatesTokenFilterFactory
ReversedWildcardFilterFactory

and for query analyze:

WhitespaceTokenizerFactory
SynonymFilterFactory
StopFilterFactory
WordDelimiterFilterFactory
LowerCaseFilterFactory
EnglishPorterFilterFactory
RemoveDuplicatesTokenFilterFactory 

I want to know which filter affecting my search result.

Answer 1

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);
        }
    }