Lucene problems searchinh hyphenated field - lucene

Question

I'm having some problems with Lucene that are driving me nuts. I have the following field:
doc.Add(new Field("cataloguenumber", i.CatalogueNumber.ToLower(), Field.Store.YES, Field.Index.ANALYZED));
Which will contain a catalogue number that looks something like this:
DF-GH5
DF-FJ4
DF-DOG
AC-DP
AC-123
AC-DOCO
i.e. two characters followed by a hyphen followed by 2-5 alphanumeric characters.
I'm trying to run a boolean query to allow users to search over the data:
// specify the search fields, lucene search in multiple fields
string[] searchfields = new string[] { "cataloguenumber", "title", "author", "categories", "year", "length", "keyword", "description" };
// Making a boolean query for searching and get the searched hits
BooleanQuery mainQuery = new BooleanQuery();
QueryParser parser;
//Add filter for main keyword
parser = new MultiFieldQueryParser(Lucene.Net.Util.Version.LUCENE_30, searchfields, new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_30));
parser.AllowLeadingWildcard = true;
mainQuery.Add(parser.Parse(GetMainSearchQueryString(SearchPhrase)), Occur.MUST);
The system is working fine for all fields EXCEPT cataloguenumber which for whatever reason is not working at all.
Ideally we would like to be able to search by full or partial cataloguenumber so for example "DF-" should return all items prefixed DF
Does anyone know how I can make this work?
Thanks very much in advance
Olly

Answer 1

A common source of problems is to use different analyzers on index-time and query-time. You should be able to get good results by using a StandardAnalyzer - it treats the text DF-GH5 as a single token so you will be able to search using fx df-gh5 or df-* but make sure to use it for the IndexWriter and the QueryParser.
Here is a simple example which builds an in-memory index with a single document, and tries to query the index by cataloguenumber.
public static void Test()
{
// Use an in-memory index.
RAMDirectory indexDirectory = new RAMDirectory();
// Make sure to use the same analyzer for indexing
Analyzer analyzer = new StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_30);
// Add single document to the index.
using (IndexWriter writer = new IndexWriter(indexDirectory, analyzer, IndexWriter.MaxFieldLength.UNLIMITED))
{
Document document = new Document();
document.Add(new Field("content", "This is just some text", Field.Store.YES, Field.Index.ANALYZED));
document.Add(new Field("cataloguenumber", "DF-GH5", Field.Store.YES, Field.Index.ANALYZED));
writer.AddDocument(document);
}
var parser = new MultiFieldQueryParser(
Lucene.Net.Util.Version.LUCENE_30,
new[] { "cataloguenumber", "content" },
analyzer);
var searcher = new IndexSearcher(indexDirectory);
DoSearch("df-gh5", parser, searcher);
DoSearch("df-*", parser, searcher);
}
private static void DoSearch(string queryString, MultiFieldQueryParser parser, IndexSearcher searcher)
{
var query = parser.Parse(queryString);
TopDocs docs = searcher.Search(query, 10);
foreach (ScoreDoc scoreDoc in docs.ScoreDocs)
{
Document searchHit = searcher.Doc(scoreDoc.Doc);
string cataloguenumber = searchHit.GetValues("cataloguenumber").FirstOrDefault();
string content = searchHit.GetValues("content").FirstOrDefault();
Console.WriteLine($"Found object: {cataloguenumber} {content}");
}
}