Some of the factors that go in to the score calculation are encoded as a byte with inevitable loss of precision. Maybe length is one of these and lucene is not differentiating between your 3 and 4 word docs. Try indexing a document that is significantly longer than 3 or 4 words.
Further reading: http://lucene.apache.org/java/3_0_3/scoring.html, the javadocs for Similarity and DefaultSimilarity, whatever Google finds. -- Ian. On Tue, Dec 28, 2010 at 8:11 PM, Qi Li <aler...@gmail.com> wrote: > Happy Holidays ! > > Test case > doc1 : test -- one two three > doc2 : test, one two three > doc3 : one two three > > Search query : "one two three" by QueryParser and StandardAnalyzer > > Question: why all of three documents have the same score? I really want > the doc3 has higher score because it is an exact match and short. Can > anybody explain this? I will appreciate a lot > > Here is my code and its output > > public class Test { > > public static void main(String[] args){ > test(); > } > > private static void test(){ > String[] contents = {"test -- one two three", > "test, one two three", > "one two three"}; > > Directory dir = new RAMDirectory(); > try { > IndexWriter writer = new IndexWriter(dir, new > StandardAnalyzer(Version.LUCENE_30), IndexWriter.MaxFieldLength.UNLIMITED); > for (int i=0; i<contents.length; i++){ > Document doc = new Document(); > doc.add(new Field("de", contents[i], Field.Store.YES, > Field.Index.ANALYZED)); > writer.addDocument(doc); > } > writer.close(); > > IndexSearcher searcher = new IndexSearcher(dir); > QueryParser parser = new QueryParser(Version.LUCENE_30,"de", new > StandardAnalyzer(Version.LUCENE_30)); > > Query q = parser.parse("one two three"); > TopDocs topDocs = searcher.search(q, 10); > for (ScoreDoc scoreDoc : topDocs.scoreDocs){ > Document doc = searcher.doc(scoreDoc.doc); > System.out.println(doc.get("de")); > Explanation explan = searcher.explain(q, scoreDoc.doc); > System.out.println(explan.toString()); > } > > } catch (CorruptIndexException e) { > e.printStackTrace(); > } catch (LockObtainFailedException e) { > e.printStackTrace(); > } catch (ParseException e) { > e.printStackTrace(); > } catch (IOException e) { > e.printStackTrace(); > } > } > } > > > test -- one two three > 0.6168854 = (MATCH) sum of: > 0.20562847 = (MATCH) weight(de:one in 0), product of: > 0.57735026 = queryWeight(de:one), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:one in 0), product of: > 1.0 = tf(termFreq(de:one)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=0) > 0.20562847 = (MATCH) weight(de:two in 0), product of: > 0.57735026 = queryWeight(de:two), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:two in 0), product of: > 1.0 = tf(termFreq(de:two)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=0) > 0.20562847 = (MATCH) weight(de:three in 0), product of: > 0.57735026 = queryWeight(de:three), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:three in 0), product of: > 1.0 = tf(termFreq(de:three)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=0) > > test, one two three > 0.6168854 = (MATCH) sum of: > 0.20562847 = (MATCH) weight(de:one in 1), product of: > 0.57735026 = queryWeight(de:one), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:one in 1), product of: > 1.0 = tf(termFreq(de:one)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=1) > 0.20562847 = (MATCH) weight(de:two in 1), product of: > 0.57735026 = queryWeight(de:two), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:two in 1), product of: > 1.0 = tf(termFreq(de:two)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=1) > 0.20562847 = (MATCH) weight(de:three in 1), product of: > 0.57735026 = queryWeight(de:three), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:three in 1), product of: > 1.0 = tf(termFreq(de:three)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=1) > > one two three > 0.6168854 = (MATCH) sum of: > 0.20562847 = (MATCH) weight(de:one in 2), product of: > 0.57735026 = queryWeight(de:one), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:one in 2), product of: > 1.0 = tf(termFreq(de:one)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=2) > 0.20562847 = (MATCH) weight(de:two in 2), product of: > 0.57735026 = queryWeight(de:two), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:two in 2), product of: > 1.0 = tf(termFreq(de:two)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=2) > 0.20562847 = (MATCH) weight(de:three in 2), product of: > 0.57735026 = queryWeight(de:three), product of: > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.8105233 = queryNorm > 0.35615897 = (MATCH) fieldWeight(de:three in 2), product of: > 1.0 = tf(termFreq(de:three)=1) > 0.71231794 = idf(docFreq=3, maxDocs=3) > 0.5 = fieldNorm(field=de, doc=2) > > Best regards, > Qi Li > --------------------------------------------------------------------- To unsubscribe, e-mail: java-user-unsubscr...@lucene.apache.org For additional commands, e-mail: java-user-h...@lucene.apache.org
