FAQ
Hello,

I ran into some very strange behavior by Lucene 1.9. Boost factor under 1.3
does not effect the result score! I wrote a simple test to isolate the
issue:

Writing test index
Creating 3 documents with same KEY and boosts of default, 1.1, 1.2, and 1.3

public static void writeTestIndex() throws IOException {

// opening index writer
IndexWriter writer = null;
writer = new IndexWriter("C:\\a_temp", new StandardAnalyzer(), true);

Document currentDocument = null;

// creating and adding document with DEFAULT boost
currentDocument = new Document();
currentDocument.add(new Field("KEY", "AA", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.add(new Field("BOOST_FACTOR", "1", Field.Store.YES,
Field.Index.UN_TOKENIZED));
writer.addDocument(currentDocument);

// creating and adding document with 1.1 boost
currentDocument = new Document();
currentDocument.add(new Field("KEY", "AA", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.add( new Field("BOOST_FACTOR", "1.1", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.setBoost((float)1.1);
writer.addDocument(currentDocument);

// creating and adding document with 1.2 boost
currentDocument = new Document();
currentDocument.add(new Field("KEY", "AA", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.add( new Field("BOOST_FACTOR", "1.2", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.setBoost((float)1.2);
writer.addDocument(currentDocument);

// creating and adding document with 1.3 boost
currentDocument = new Document();
currentDocument.add(new Field("KEY", "AA", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.add(new Field("BOOST_FACTOR", "1.3", Field.Store.YES,
Field.Index.UN_TOKENIZED));
currentDocument.setBoost((float)1.3);
writer.addDocument(currentDocument);

// optimizing and closing IndexWriter
writer.optimize();
writer.close();
}


Test Search
Searching for the KEY value, which is the same in all 4 documents

public static void testIndex() throws IOException {

// opening IndexSearcher
IndexSearcher searcher = null;
searcher = new IndexSearcher("C:\\a_temp");

// searching for KEY
Hits hits = searcher.search(new TermQuery(new Term("KEY", "AA")));

// listing documents and their BOOST_FACTOR field
Document doc = null;
if (null != hits) {
logger.debug("Listing results: ");
for (int i = 0; i < hits.length(); i++) {
doc = hits.doc(i);
logger.debug("BOOST_FACTOR field: " + doc.get("BOOST_FACTOR") + " Score:
" + hits.score(i));
}
}

// closing IndexSearcher
searcher.close();
}

Output

BOOST_FACTOR field: 1.3 Score: 0.9710705
BOOST_FACTOR field: 1 Score: 0.7768564
BOOST_FACTOR field: 1.1 Score: 0.7768564
BOOST_FACTOR field: 1.2 Score: 0.7768564

Boost of 1.1 and 1.2 did not effect score for the last 2 documents!
Document with boost of 1.3 jumped to the top, but the rest were returned in
the order they were added to the index.

What am I missing here? I thought document score would reflect all levels
of boost, not just 1.3 and above? Please help.
--
View this message in context: http://www.nabble.com/Boosting-Documents-and-score-calculation-tf2159899.html#a5968287
Sent from the Lucene - Java Users forum at Nabble.com.


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groupjava-user @
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postedAug 24, '06 at 5:07p
activeAug 24, '06 at 11:04p
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websitelucene.apache.org

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