Paging using Lucene.net

Question

I\'m working on a .Net application which uses Asp.net 3.5 and Lucene.Net I am showing search results given by Lucene.Net in an asp.net datagrid. I need to implement Paging (10 r

Answer 1

What I do is iterate through the hits and insert them into a temporary table in the db. Then I can run a regular SQL query - joining that temp table with other tables too - and give the grid the DataSet/DataView that it wants.

Note that I do the inserts and the query in ONE TRIP to the db, because I'm using just one SQL batch.

void Page_Load(Object sender, EventArgs e)
{

    dbutil = new DbUtil();
    security = new Security();
    security.check_security(dbutil, HttpContext.Current, Security.ANY_USER_OK);

    Lucene.Net.Search.Query query = null;

    try
    {
        if (string.IsNullOrEmpty(Request["query"]))
        {
            throw new Exception("You forgot to enter something to search for...");
        }

        query = MyLucene.parser.Parse(Request["query"]);

    }
    catch (Exception e3)
    {
        display_exception(e3);
    }


    Lucene.Net.Highlight.QueryScorer scorer = new Lucene.Net.Highlight.QueryScorer(query);
    Lucene.Net.Highlight.Highlighter highlighter = new Lucene.Net.Highlight.Highlighter(MyLucene.formatter, scorer);
    highlighter.SetTextFragmenter(MyLucene.fragmenter); // new Lucene.Net.Highlight.SimpleFragmenter(400));

    StringBuilder sb = new StringBuilder();
    string guid = Guid.NewGuid().ToString().Replace("-", "");
    Dictionary dict_already_seen_ids = new Dictionary();

    sb.Append(@"
create table #$GUID
(
temp_bg_id int,
temp_bp_id int,
temp_score float,
temp_text nvarchar(3000)
)
    ");

    lock (MyLucene.my_lock)
    {

        Lucene.Net.Search.Hits hits = null;
        try
        {
            hits = MyLucene.search(query);
        }
        catch (Exception e2)
        {
            display_exception(e2);
        }

        // insert the search results into a temp table which we will join with what's in the database
        for (int i = 0; i < hits.Length(); i++)
        {
            if (dict_already_seen_ids.Count < 100)
            {
                Lucene.Net.Documents.Document doc = hits.Doc(i);
                string bg_id = doc.Get("bg_id");
                if (!dict_already_seen_ids.ContainsKey(bg_id))
                {
                    dict_already_seen_ids[bg_id] = 1;
                    sb.Append("insert into #");
                    sb.Append(guid);
                    sb.Append(" values(");
                    sb.Append(bg_id);
                    sb.Append(",");
                    sb.Append(doc.Get("bp_id"));
                    sb.Append(",");
                    //sb.Append(Convert.ToString((hits.Score(i))));
                    sb.Append(Convert.ToString((hits.Score(i))).Replace(",", "."));  // Somebody said this fixes a bug. Localization issue?
                    sb.Append(",N'");

                    string raw_text = Server.HtmlEncode(doc.Get("raw_text"));
                    Lucene.Net.Analysis.TokenStream stream = MyLucene.anal.TokenStream("", new System.IO.StringReader(raw_text));
                    string highlighted_text = highlighter.GetBestFragments(stream, raw_text, 1, "...").Replace("'", "''");
                    if (highlighted_text == "") // someties the highlighter fails to emit text...
                    {
                        highlighted_text = raw_text.Replace("'","''");
                    }
                    if (highlighted_text.Length > 3000)
                    {
                        highlighted_text = highlighted_text.Substring(0,3000);
                    }
                    sb.Append(highlighted_text);
                    sb.Append("'");
                    sb.Append(")\n");
                }
            }
            else
            {
                break;
            }
        }
        //searcher.Close();
    }