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From John Griffin <jgrif...@thebluezone.net>
Subject Re: Document boost, is it working?
Date Tue, 30 Oct 2007 21:40:14 GMT
Bruno Dery wrote:
> Hi all the following is using Lucene  2.2.0. 
>  
> I've been trying to alter the scoring of my search results to boost by
> date. My idea was to boost documents while indexing using the date but
> it doesn't work. So I put together this little sample piece of code to
> investigate further and apparently setting the document boost does
> nothing. In my example below, you'd expect the display the output 20 2
> and 10 but I get 1 1 1. Is this normal behavior and if so how am I
> supposed to use document boosting because it seems like I'm missing
> something...
>  
> Here's the sample  of code:
>  
> -----------
>  
>  
> import org.apache.lucene.analysis.standard.StandardAnalyzer;
>
> import org.apache.lucene.document.Document;
>
> import org.apache.lucene.document.Field;
>
> import org.apache.lucene.index.IndexReader;
>
> import org.apache.lucene.index.IndexWriter;
>
> import org.apache.lucene.store.FSDirectory;
>
> public class IndexTest {
>
> /**
>
> * @param args
>
> */
>
> public static void main(String[] args) throws Exception {
>
> // Create bogus index 
>
> IndexWriter writer = new
> IndexWriter(FSDirectory.getDirectory("C:/lucene_test/"), new
> StandardAnalyzer(), true);
>
> writer.setUseCompoundFile(true);
>
> Document doc = new Document();
>
> doc.add(new Field("testfield", "high ranking", Field.Store.YES,
> Field.Index.TOKENIZED));
>
> doc.setBoost(20);
>
> writer.addDocument(doc);
>
> doc = new Document();
>
> doc.add(new Field("testfield", "low ranking", Field.Store.YES,
> Field.Index.TOKENIZED));
>
> doc.setBoost(2);
>
> writer.addDocument(doc);
>
> doc = new Document();
>
> doc.add(new Field("testfield", "mid ranking", Field.Store.YES,
> Field.Index.TOKENIZED));
>
> doc.setBoost(10);
>
> writer.addDocument(doc);
>
> writer.close();
>
> // Read bogus index 
>
> IndexReader reader =
> IndexReader.open(FSDirectory.getDirectory("C:/lucene_test/"));
>
> System.out.println(reader.document(0).getBoost());
>
> System.out.println(reader.document(1).getBoost());
>
> System.out.println(reader.document(2).getBoost());
>
> }
>
> }
>
>  
>  
>  
>
>   
Bruno,

After your comment // read bogus index, replace your code with this.

      IndexSearcher searcher = new 
IndexSearcher("/home/griffij/lucene_test/");
      final QueryParser parser = new QueryParser("testfield", new 
StandardAnalyzer());
      final Query query = parser.parse("ranking");
      Hits hits = searcher.search(query);
      for (int x = 0; x < hits.length(); x++)
      {
         System.out.println(hits.doc(x) + "score=> " + hits.score(x));
      }


You'll see that the boost does indeed take effect. The boost value isn't 
stored with the document you set it against. It takes effect during the 
scoring process and effects all fields in the document.

John G.


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