c# - Lucene.net range queries + highlighting

Question

Yet another Lucene.net question by an extreme newbie to it.

This time, I have found an interesting issue with using a query that contains a range and using highlighting.

I am writing this from memory, so please forgive any syntax errors.

I have a hypothetical Lucene index of this:

---------------------------------------------------------
|       date         |               text               |
---------------------------------------------------------
|     1317809124     |       a crazy block of text      |
---------------------------------------------------------
|     1317809284     |       programmers are crazy      |
---------------------------------------------------------

** date is a unix timestamp        

... and they have been added to the index via this:

Lucene.Net.Documents.Document doc = new Lucene.Net.Documents.Document();
doc.Add(new Lucene.Net.Documents.Field("text", "some block of text", Lucene.Net.Documents.Field.Store.YES, Lucene.Net.Documents.Field.Index.ANALYZED, Lucene.Net.Documents.Field.TermVector.WITH_POSITIONS_OFFSETS));
doc.Add(new Lucene.Net.Documents.Field("date", "some unix timestamp", Lucene.Net.Documents.Field.Store.YES, Lucene.Net.Documents.Field.Index.NOT_ANALYZED));

This is how I am querying Lucene:

Lucene.Net.Analysis.Standard.StandardAnalyzer analyzer = new Lucene.Net.Analysis.Standard.StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_29);
Lucene.Net.Search.IndexSearcher searcher = new Lucene.Net.Search.IndexSearcher(Lucene.Net.Store.FSDirectory.Open(_headlinesDirectory), true);
Lucene.Net.QueryParsers.QueryParser parser = new Lucene.Net.QueryParsers.QueryParser(Lucene.Net.Util.Version.LUCENE_29, "text", analyzer);
Lucene.Net.Search.Query query = parser.Parse(queryPhrase);
Lucene.Net.Search.Hits hits = searcher.Search(query);

// code highlighting
Lucene.Net.Highlight.Formatter formatter = new Lucene.Net.Highlight.SimpleHTMLFormatter("<span style="background:yellow;">","</span>");
Lucene.Net.Highlight.SimpleFragmenter fragmenter = new Lucene.Net.Highlight.SimpleFragmenter(50);
Lucene.Net.Highlight.QueryScorer scorer = new Lucene.Net.Highlight.QueryScorer(query);
Lucene.Net.Highlight.Highlighter highlighter = new Lucene.Net.Highlight.Highlighter(formatter, scorer);
highlighter.SetTextFragmenter(fragmenter);     

for (int i = 0; i < hits.Length(); i++)
{
    Lucene.Net.Documents.Document doc = hits.Doc(i);
    Lucene.Net.Analysis.TokenStream stream = analyzer.TokenStream("", new StringReader(doc.Get("text")));
    string highlightedText = highlighter.GetBestFragments(stream, doc.Get("text"), 1, "...");
    Console.WriteLine("--> " + highlightedText);
}

Here is an example of my query:

crazy AND date:[1286273266 TO 32503680000]

When this is queried, it finds all the results for "crazy" but does not output any highlighted text.

When the date range is removed and you simply query the term:

crazy

... this time highlighting works properly.

Is there something I am doing wrong in my implementation, should I be looking at a new implementation, or is this a known issue with potentially a work around.

Thank you in advance stackeroverflow'ers :)

-- EDIT --

I have implemented the suggestions from LB (amazing btw!). I still have no idea why this works as I think Lucene is complete voodoo or programming witchcraft, but it does and I am happy :).

For completeness, here is the modified code:

Lucene.Net.Analysis.Standard.StandardAnalyzer analyzer = new Lucene.Net.Analysis.Standard.StandardAnalyzer(Lucene.Net.Util.Version.LUCENE_29);
Lucene.Net.Search.IndexSearcher searcher = new Lucene.Net.Search.IndexSearcher(Lucene.Net.Store.FSDirectory.Open(_headlinesDirectory), true);
Lucene.Net.QueryParsers.QueryParser parser = new Lucene.Net.QueryParsers.QueryParser(Lucene.Net.Util.Version.LUCENE_29, "text", analyzer);

// new line here
parser.SetMultiTermRewriteMethod(Lucene.Net.Search.MultiTermQuery.SCORING_BOOLEAN_QUERY_REWRITE);

Lucene.Net.Search.Query query = parser.Parse(queryPhrase);

// new line here
Lucene.Net.Search.Query query2 = query.Rewrite(searcher.GetIndexReader());
Lucene.Net.Search.Hits hits = searcher.Search(query);

// code highlighting
Lucene.Net.Highlight.Formatter formatter = new Lucene.Net.Highlight.SimpleHTMLFormatter("<span style="background:yellow;">","</span>");
Lucene.Net.Highlight.SimpleFragmenter fragmenter = new Lucene.Net.Highlight.SimpleFragmenter(50);

// changed to use query2
Lucene.Net.Highlight.QueryScorer scorer = new Lucene.Net.Highlight.QueryScorer(query2);

Lucene.Net.Highlight.Highlighter highlighter = new Lucene.Net.Highlight.Highlighter(formatter, scorer);
highlighter.SetTextFragmenter(fragmenter);

for (int i = 0; i < hits.Length(); i++)
{
    Lucene.Net.Documents.Document doc = hits.Doc(i);
    Lucene.Net.Analysis.TokenStream stream = analyzer.TokenStream("", new StringReader(doc.Get("text")));
    string highlightedText = highlighter.GetBestFragments(stream, doc.Get("text"), 1, "...");
    Console.WriteLine("--> " + highlightedText);
}

If you could, let me know if I have implemented the suggestions accurately.

Answer 1

First invoke QueryParser's

SetMultiTermRewriteMethod(MultiTermQuery.SCORING_BOOLEAN_QUERY_REWRITE)

method, then create a new query as

Query newQuery = query.Rewrite(indexReader);

Now you can use "newQuery" to make your searches.