No hits when searching for “mvc2” with lucene.net

Question

I am indexing and searching with lucene.net, the only problem I am having with my code is that it does not find any hits when searching for "mvc2"(it seems to work with all the other words I search), I have tried a different analyzer(see comments by analyzer) and older lucene code, here is my index and search code, I would really appreciate if someone can show me where I am going wrong with this, Thanks.

////Indexing code
public void DoIndexing(string CvContent)
    {
        //state the file location of the index
        const string indexFileLocation = @"C:\RecruitmentIndexer\IndexedCVs";

        //if directory does not exist, create it, and create new index for it.
        //if directory does exist, do not create directory, do not create new      //index(add field to previous index).
        bool creatNewDirectory;   //to pass into lucene GetDirectory
        bool createNewIndex;      //to pass into lucene indexWriter
        if (!Directory.Exists(indexFileLocation))
        {
            creatNewDirectory = true;
            createNewIndex = true;
        }
        else
        {
            creatNewDirectory = false;
            createNewIndex = false;
        }


        Lucene.Net.Store.Directory dir =
            Lucene.Net.Store.FSDirectory.GetDirectory(indexFileLocation, creatNewDirectory);//creates if true

        //create an analyzer to process the text
        Lucene.Net.Analysis.Analyzer analyzer = new
        Lucene.Net.Analysis.SimpleAnalyzer();              //this analyzer gets all //hits exept mvc2 
        //Lucene.Net.Analysis.Standard.StandardAnalyzer(); //this leaves out sql once //and mvc2 once

        //create the index writer with the directory and analyzer defined.
        Lucene.Net.Index.IndexWriter indexWriter = new
        Lucene.Net.Index.IndexWriter(dir, analyzer,
            /*true to create a new index*/ createNewIndex);

        //create a document, add in a single field
        Lucene.Net.Documents.Document doc = new
        Lucene.Net.Documents.Document();



        Lucene.Net.Documents.Field fldContent =
          new Lucene.Net.Documents.Field("content",
          CvContent,//"This is some text to search by indexing",
          Lucene.Net.Documents.Field.Store.YES,
        Lucene.Net.Documents.Field.Index.ANALYZED,
        Lucene.Net.Documents.Field.TermVector.YES);

        doc.Add(fldContent);

        //write the document to the index
        indexWriter.AddDocument(doc);

        //optimize and close the writer
        indexWriter.Optimize();
        indexWriter.Close();

    }

////search code
private void button2_Click(object sender, EventArgs e)
    {

        string SearchString = textBox1.Text;

        ///after creating an index, search
        //state the file location of the index
        const string indexFileLocation = @"C:\RecruitmentIndexer\IndexedCVs";

        Lucene.Net.Store.Directory dir =
        Lucene.Net.Store.FSDirectory.GetDirectory(indexFileLocation, false);

        //create an index searcher that will perform the search
        Lucene.Net.Search.IndexSearcher searcher = new
        Lucene.Net.Search.IndexSearcher(dir);

        SearchString = SearchString.Trim();
        SearchString = QueryParser.Escape(SearchString);


        //build a query object
        Lucene.Net.Index.Term searchTerm =
          new Lucene.Net.Index.Term("content", SearchString);
        Lucene.Net.Search.Query query = new Lucene.Net.Search.TermQuery(searchTerm);

        //execute the query
        Lucene.Net.Search.Hits hits = searcher.Search(query);

        label1.Text = hits.Length().ToString();

        //iterate over the results.
        for (int i = 0; i < hits.Length(); i++)
        {
           Lucene.Net.Documents.Document docMatch = hits.Doc(i);

            MessageBox.Show(docMatch.Get("content"));

        }

    }

Answer 1

I believe that StandardAnalyzer actually strips out "2" from "mvc2", leaving the indexed word to be only "mvc". I'm not sure about SimpleAnalyzer though. You could try to use WhitespaceAnalyzer, which I believe doesn't strip out numbers.

You should also process your search input the same way that you process indexing. A TermQuery is a "identical" match, which means that you if you try to search for "mvc2" where the actual strings in your index always says "mvc", then you won't get a match.

I haven't found a way to actually make use of an analyzer unless I use the QueryParser, and even then I always had odd results.

You could try this in order to "tokenize" your search string in the same way as you index your document, and make a boolean AND search on all terms:

    // We use a boolean query to combine all prefix queries
    var analyzer = new SimpleAnalyzer();
    var query = new BooleanQuery();

    using ( var reader = new StringReader( queryTerms ) )
    {
        // This is what we need to do in order to get the terms one by one, kind of messy but seemed to be the only way
        var tokenStream = analyzer.TokenStream( "why_do_I_need_this", reader );
        var termAttribute = tokenStream.GetAttribute( typeof( TermAttribute ) ) as TermAttribute;

        // This will return false when all tokens has been processed.
        while ( tokenStream.IncrementToken() )
        {
            var token = termAttribute.Term();
            query.Add( new PrefixQuery( new Term( KEYWORDS_FIELD_NAME, token ) ), BooleanClause.Occur.MUST );
        }

        // I don't know if this is necessary, but can't hurt
        tokenStream.Close();
    }

You can replace the PrefixQuery with TermQuery if you only want full matches (PrefixQuery would match anything starting with, "search*")