Question

I am having trouble searching for an exact phrase using Lucene.NET 2.0.0.4

For example I am searching for “scope attribute sets the variable” (including quotes) but receive no matches, I have confirmed 100% that the phrase exists.

Can anyone suggest where I am going wrong? Is this even supported with Lucene.NET? As usual the API documentation is not too helpful and a few CodeProject articles I’ve read don’t specifically touch on this.

Using the following code to create the index:

Directory dir = Lucene.Net.Store.FSDirectory.GetDirectory("Index", true);

Analyzer analyzer = new Lucene.Net.Analysis.SimpleAnalyzer();

IndexWriter indexWriter = new Lucene.Net.Index.IndexWriter(dir, analyzer,true);

//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", File.ReadAllText(@"Documents\100.txt"),
    Lucene.Net.Documents.Field.Store.YES,
    Lucene.Net.Documents.Field.Index.TOKENIZED);

doc.Add(fldContent);

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

I then search for a phrase using:

//state the file location of the index
Directory dir = Lucene.Net.Store.FSDirectory.GetDirectory("Index", false);

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

QueryParser qp = new QueryParser("content", new SimpleAnalyzer());

// txtSearch.Text  Contains a phrase such as "this is a phrase" 
Query q=qp.Parse(txtSearch.Text);  


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

The target document is about 7 MB plain text.

I have seen this previous question however I don’t want a proximity search, just an exact phrase search.

Answer 1

You have not enabled the term positions. Creating field as follows should solve your problem.

Lucene.Net.Documents.Field fldContent = 
    new Lucene.Net.Documents.Field("content", 
        File.ReadAllText(@"Documents\100.txt"),
    Lucene.Net.Documents.Field.Store.YES,
    Lucene.Net.Documents.Field.Index.TOKENIZED, 
    Lucene.Net.Documents.Field.TermVector.WITH_POSITIONS_OFFSETS);