Lucene 3.0.2 Query.setBoost() 问题

在Lucene 3.0.2中，在Field 、 Document 和 Query中都有setBoost接口，但是为什么在Query中设置boost值，在搜索结果中却没有任何变化呢？求高人指教啊。。。 代码如下：

package com.eric.lucene;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.Version;

public class ScoreSortTest {
	public static void main(String[] args) throws Exception {
		Directory dir = new RAMDirectory();
		IndexWriter writer = new IndexWriter(dir, new StandardAnalyzer(Version.LUCENE_30), true, IndexWriter.MaxFieldLength.LIMITED);
		
		Document doc1 = new Document();
		Document doc2 = new Document();
		Document doc3 = new Document();
		
		doc1.add(new Field("bookname","thinking in java", Field.Store.YES, Field.Index.ANALYZED));
		doc2.add(new Field("bookname","thinking in java java java", Field.Store.YES, Field.Index.ANALYZED));
		doc3.add(new Field("bookname","thinking in c++", Field.Store.YES, Field.Index.ANALYZED));
		
		writer.addDocument(doc1);
		writer.addDocument(doc2);
		writer.addDocument(doc3);
		
		writer.optimize();
		writer.close();
		
		IndexSearcher searcher = new IndexSearcher(dir);
		Query query = new TermQuery(new Term("bookname","java"));
//		query.setBoost(2);
		
		TopScoreDocCollector collector = TopScoreDocCollector.create(100, false);
		searcher.search(query, collector);
		
		ScoreDoc[] hits = collector.topDocs().scoreDocs;
		for(int i=0; i<hits.length;i++){
			Document doc = searcher.doc(hits[i].doc);
			System.out.println(doc.getBoost());
			System.out.print(doc.get("bookname") + "\t\t");
			System.out.println(hits[i].score);
			System.out.println(searcher.explain(query, hits[i].doc));
		}
	}
}

在没有query.setBoost(2);的情况下，结果如下：

引用

1.0
thinking in java java java 0.8660254
0.8660254 = (MATCH) fieldWeight(bookname:java in 1), product of:
  1.7320508 = tf(termFreq(bookname:java)=3)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.5 = fieldNorm(field=bookname, doc=1)

1.0
thinking in java 0.625
0.625 = (MATCH) fieldWeight(bookname:java in 0), product of:
  1.0 = tf(termFreq(bookname:java)=1)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.625 = fieldNorm(field=bookname, doc=0)

在有query.setBoost(2);的情况下，结果如下：

引用

1.0
thinking in java java java 0.8660254
0.8660254 = (MATCH) fieldWeight(bookname:java in 1), product of:
  1.7320508 = tf(termFreq(bookname:java)=3)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.5 = fieldNorm(field=bookname, doc=1)

1.0
thinking in java 0.625
0.625 = (MATCH) fieldWeight(bookname:java in 0), product of:
  1.0 = tf(termFreq(bookname:java)=1)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.625 = fieldNorm(field=bookname, doc=0)

在Field和Document中setBoost的值，在搜索结果中是有变化的。(因为Field都相同，没有进行尝试，但和Document一样，都是将boost值设置到了索引中)。代码如下：

package com.eric.lucene;

import org.apache.lucene.analysis.standard.StandardAnalyzer;
import org.apache.lucene.document.Document;
import org.apache.lucene.document.Field;
import org.apache.lucene.index.IndexWriter;
import org.apache.lucene.index.Term;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.Query;
import org.apache.lucene.search.ScoreDoc;
import org.apache.lucene.search.TermQuery;
import org.apache.lucene.search.TopScoreDocCollector;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.RAMDirectory;
import org.apache.lucene.util.Version;

public class ScoreSortTest {
	public static void main(String[] args) throws Exception {
		Directory dir = new RAMDirectory();
		IndexWriter writer = new IndexWriter(dir, new StandardAnalyzer(Version.LUCENE_30), true, IndexWriter.MaxFieldLength.LIMITED);
		
		Document doc1 = new Document();
		Document doc2 = new Document();
		Document doc3 = new Document();
		
		doc1.add(new Field("bookname","thinking in java", Field.Store.YES, Field.Index.ANALYZED));
		doc1.setBoost(4);
		doc2.add(new Field("bookname","thinking in java java java", Field.Store.YES, Field.Index.ANALYZED));
		doc3.add(new Field("bookname","thinking in c++", Field.Store.YES, Field.Index.ANALYZED));
		
		writer.addDocument(doc1);
		writer.addDocument(doc2);
		writer.addDocument(doc3);
		
		writer.optimize();
		writer.close();
		
		IndexSearcher searcher = new IndexSearcher(dir);
		Query query = new TermQuery(new Term("bookname","java"));
		
		TopScoreDocCollector collector = TopScoreDocCollector.create(100, false);
		searcher.search(query, collector);
		
		ScoreDoc[] hits = collector.topDocs().scoreDocs;
		for(int i=0; i<hits.length;i++){
			Document doc = searcher.doc(hits[i].doc);
			System.out.println(doc.getBoost());
			System.out.print(doc.get("bookname") + "\t\t");
			System.out.println(hits[i].score);
			System.out.println(searcher.explain(query, hits[i].doc));
		}
	}
}

在没有doc1.setBoost(4);这一行的时候，结果如下：

引用

1.0
thinking in java java java 0.8660254
0.8660254 = (MATCH) fieldWeight(bookname:java in 1), product of:
  1.7320508 = tf(termFreq(bookname:java)=3)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.5 = fieldNorm(field=bookname, doc=1)

1.0
thinking in java 0.625
0.625 = (MATCH) fieldWeight(bookname:java in 0), product of:
  1.0 = tf(termFreq(bookname:java)=1)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.625 = fieldNorm(field=bookname, doc=0)

在有doc1.setBoost(4);这一行的时候，结果如下：

引用

1.0
thinking in java 2.5
2.5 = (MATCH) fieldWeight(bookname:java in 0), product of:
  1.0 = tf(termFreq(bookname:java)=1)
  1.0 = idf(docFreq=2, maxDocs=3)
  2.5 = fieldNorm(field=bookname, doc=0)

1.0
thinking in java java java 0.8660254
0.8660254 = (MATCH) fieldWeight(bookname:java in 1), product of:
  1.7320508 = tf(termFreq(bookname:java)=3)
  1.0 = idf(docFreq=2, maxDocs=3)
  0.5 = fieldNorm(field=bookname, doc=1)