Using a Combination of Wildcards and Stemming

Question

I\'m using a snowball analyzer to stem the titles of multiple documents. Everything works well, but their are some quirks.

Example:

A search for \"valv\", \

Answer 1

I don't think that there is an easy(and correct) way to do this.

My solution would be writing a custom query parser that finds the longest string common to the terms in the index and to your search criteria.

class MyQueryParser : Lucene.Net.QueryParsers.QueryParser
{
    IndexReader _reader;
    Analyzer _analyzer;

    public MyQueryParser(string field, Analyzer analyzer,IndexReader indexReader) : base(field, analyzer)
    {
        _analyzer = analyzer;
        _reader = indexReader;
    }

    public override Query GetPrefixQuery(string field, string termStr)
    {
        for(string longestStr = termStr; longestStr.Length>2; longestStr = longestStr.Substring(0,longestStr.Length-1))
        {
            TermEnum te = _reader.Terms(new Term(field, longestStr));
            Term term = te.Term();
            te.Close();
            if (term != null && term.Field() == field && term.Text().StartsWith(longestStr))
            {
                return base.GetPrefixQuery(field, longestStr);
            }
        }

        return base.GetPrefixQuery(field, termStr);
    }
}

you can also try to call your analyzer in GetPrefixQuery which is not called for PrefixQuerys

TokenStream ts = _analyzer.TokenStream(field, new StringReader(termStr));
Lucene.Net.Analysis.Token token = ts.Next();
var termstring = token.TermText();
ts.Close();
return base.GetPrefixQuery(field, termstring);

But, be aware that you can always find a case where the returned results are not correct. This is why Lucene doesn't take analyzers into account when using wildcards.