docs/attachments/LUCENE-1272/morelikethis_boostfactor.patch

Index: contrib/queries/src/test/org/apache/lucene/search/similar/TestMoreLikeThis.java
===================================================================
--- contrib/queries/src/test/org/apache/lucene/search/similar/TestMoreLikeThis.java	(revision 0)
+++ contrib/queries/src/test/org/apache/lucene/search/similar/TestMoreLikeThis.java	(revision 0)
@@ -0,0 +1,110 @@
+package org.apache.lucene.search.similar;
+
+import java.io.IOException;
+import java.io.StringReader;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+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.index.IndexWriter.MaxFieldLength;
+import org.apache.lucene.search.BooleanClause;
+import org.apache.lucene.search.BooleanQuery;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.TermQuery;
+import org.apache.lucene.store.RAMDirectory;
+import org.apache.lucene.util.LuceneTestCase;
+
+public class TestMoreLikeThis extends LuceneTestCase {
+    private static final String KEY_FIELD = "url";
+    private RAMDirectory directory;
+    private IndexReader reader;
+    private IndexSearcher searcher;
+
+    protected void setUp() throws Exception {
+	directory = new RAMDirectory();
+	IndexWriter writer = new IndexWriter(directory, new StandardAnalyzer(),
+		true, MaxFieldLength.UNLIMITED);
+
+	// Add series of docs with specific information for MoreLikeThis
+	addDoc(writer, "lucene");
+	addDoc(writer, "lucene release");
+
+	writer.close();
+	reader = IndexReader.open(directory, true);
+	searcher = new IndexSearcher(reader);
+
+    }
+
+    protected void tearDown() throws Exception {
+	reader.close();
+	searcher.close();
+	directory.close();
+    }
+
+    private void addDoc(IndexWriter writer, String text) throws IOException {
+	Document doc = new Document();
+	doc.add(new Field("text", text, Field.Store.YES, Field.Index.ANALYZED));
+	writer.addDocument(doc);
+    }
+
+    public void testBoostFactor() throws Throwable {
+	Map originalValues = getOriginalValues();
+
+	MoreLikeThis mlt = new MoreLikeThis(
+		reader);
+	mlt.setMinDocFreq(1);
+	mlt.setMinTermFreq(1);
+	mlt.setMinWordLen(1);
+	mlt.setFieldNames(new String[] { "text" });
+	mlt.setBoost(true);
+
+	// this mean that every term boost factor will be multiplied by this
+	// number
+	float boostFactor = 5;
+	mlt.setBoostFactor(boostFactor);
+
+	BooleanQuery query = (BooleanQuery) mlt.like(new StringReader(
+		"lucene release"));
+	List clauses = query.clauses();
+
+	assertEquals("Expected " + originalValues.size() + " clauses.",
+		originalValues.size(), clauses.size());
+
+	for (int i = 0; i < clauses.size(); i++) {
+	    BooleanClause clause = (BooleanClause) clauses.get(i);
+	    TermQuery tq = (TermQuery) clause.getQuery();
+	    Float termBoost = (Float) originalValues.get(tq.getTerm().text());
+	    assertNotNull("Expected term " + tq.getTerm().text(), termBoost);
+
+	    float totalBoost = termBoost.floatValue() * boostFactor;
+	    assertTrue("Expected boost of " + totalBoost + " for term '"
+		    + tq.getTerm().text() + "' got " + tq.getBoost(),
+		    totalBoost == tq.getBoost());
+	}
+    }
+
+    private Map getOriginalValues() throws IOException {
+	Map originalValues = new HashMap();
+	MoreLikeThis mlt = new MoreLikeThis(reader);
+	mlt.setMinDocFreq(1);
+	mlt.setMinTermFreq(1);
+	mlt.setMinWordLen(1);
+	mlt.setFieldNames(new String[] { "text" });
+	mlt.setBoost(true);
+	BooleanQuery query = (BooleanQuery) mlt.like(new StringReader(
+		"lucene release"));
+	List clauses = query.clauses();
+
+	for (int i = 0; i < clauses.size(); i++) {
+	    BooleanClause clause = (BooleanClause) clauses.get(i);
+	    TermQuery tq = (TermQuery) clause.getQuery();
+	    originalValues.put(tq.getTerm().text(), new Float(tq.getBoost()));
+	}
+	return originalValues;
+    }
+}
Index: contrib/queries/src/java/org/apache/lucene/search/similar/MoreLikeThis.java
===================================================================
--- contrib/queries/src/java/org/apache/lucene/search/similar/MoreLikeThis.java	(revision 781362)
+++ contrib/queries/src/java/org/apache/lucene/search/similar/MoreLikeThis.java	(working copy)
@@ -282,6 +282,27 @@
     private final IndexReader ir;
 
     /**
+     * Boost factor to use when boosting the terms
+     */
+    private float boostFactor = 1;
+
+    /**
+     * Returns the boost factor used when boosting terms
+     * @return the boost factor used when boosting terms
+     */
+    public float getBoostFactor() {
+        return boostFactor;
+    }
+
+    /**
+     * Sets the boost factor to use when boosting terms
+     * @param boostFactor
+     */
+    public void setBoostFactor(float boostFactor) {
+        this.boostFactor = boostFactor;
+    }
+
+    /**
      * Constructor requiring an IndexReader.
      */
     public MoreLikeThis(IndexReader ir) {
@@ -586,7 +607,7 @@
                 }
                 float myScore = ((Float) ar[2]).floatValue();
 
-                tq.setBoost(myScore / bestScore);
+                tq.setBoost(boostFactor * myScore / bestScore);
             }
 
             try {