LUCENE-2785: add new TotalHitCountCollector (only counts hits); don't allow numHits=0 to TSDC or TFC

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/trunk@1040935 13f79535-47bb-0310-9956-ffa450edef68

lucene/src/java/org/apache/lucene/search/IndexSearcher.java

@@ -158,11 +158,11 @@ public class IndexSearcher extends Searcher {
   @Override
   public TopDocs search(Weight weight, Filter filter, int nDocs) throws IOException {
 
-    if (nDocs <= 0) {
-      throw new IllegalArgumentException("nDocs must be > 0");
+    int limit = reader.maxDoc();
+    if (limit == 0) {
+      limit = 1;
     }
-
-    nDocs = Math.min(nDocs, reader.maxDoc());
+    nDocs = Math.min(nDocs, limit);
 
     TopScoreDocCollector collector = TopScoreDocCollector.create(nDocs, !weight.scoresDocsOutOfOrder());
     search(weight, filter, collector);
@@ -190,7 +190,11 @@ public class IndexSearcher extends Searcher {
                              Sort sort, boolean fillFields)
       throws IOException {
 
-    nDocs = Math.min(nDocs, reader.maxDoc());
+    int limit = reader.maxDoc();
+    if (limit == 0) {
+      limit = 1;
+    }
+    nDocs = Math.min(nDocs, limit);
 
     TopFieldCollector collector = TopFieldCollector.create(sort, nDocs,
         fillFields, fieldSortDoTrackScores, fieldSortDoMaxScore, !weight.scoresDocsOutOfOrder());

lucene/src/java/org/apache/lucene/search/TopFieldCollector.java

@@ -913,6 +913,10 @@ public abstract class TopFieldCollector extends TopDocsCollector<Entry> {
       throw new IllegalArgumentException("Sort must contain at least one field");
     }
     
+    if (numHits <= 0) {
+      throw new IllegalArgumentException("numHits must be > 0; please use TotalHitCountCollector if you just need the total hit count");
+    }
+
     FieldValueHitQueue queue = FieldValueHitQueue.create(sort.fields, numHits);
     if (queue.getComparators().length == 1) {
       if (docsScoredInOrder) {

lucene/src/java/org/apache/lucene/search/TopScoreDocCollector.java

@@ -109,6 +109,10 @@ public abstract class TopScoreDocCollector extends TopDocsCollector<ScoreDoc> {
    */
   public static TopScoreDocCollector create(int numHits, boolean docsScoredInOrder) {
     
+    if (numHits <= 0) {
+      throw new IllegalArgumentException("numHits must be > 0; please use TotalHitCountCollector if you just need the total hit count");
+    }
+
     if (docsScoredInOrder) {
       return new InOrderTopScoreDocCollector(numHits);
     } else {

lucene/src/java/org/apache/lucene/search/TotalHitCountCollector.java

@@ -0,0 +1,47 @@
+package org.apache.lucene.search;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import org.apache.lucene.index.IndexReader;
+
+/**
+ * Just counts the total number of hits.
+ */
+
+public class TotalHitCountCollector extends Collector {
+  private int totalHits;
+
+  /** Returns how many hits matched the search. */
+  public int getTotalHits() {
+    return totalHits;
+  }
+
+  public void setScorer(Scorer scorer) {
+  }
+
+  public void collect(int doc) {
+    totalHits++;
+  }
+
+  public void setNextReader(IndexReader reader, int docBase) {
+  }
+
+  public boolean acceptsDocsOutOfOrder() {
+    return true;
+  }
+}

lucene/src/test/org/apache/lucene/search/TestSort.java

@@ -26,9 +26,6 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Locale;
 
-import junit.framework.Test;
-import junit.framework.TestSuite;
-
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
@@ -1104,7 +1101,7 @@ public class TestSort extends LuceneTestCase implements Serializable {
   private void assertMatches(String msg, Searcher searcher, Query query, Sort sort,
       String expectedResult) throws IOException {
     //ScoreDoc[] result = searcher.search (query, null, 1000, sort).scoreDocs;
-    TopDocs hits = searcher.search (query, null, expectedResult.length(), sort);
+    TopDocs hits = searcher.search (query, null, Math.max(1, expectedResult.length()), sort);
     ScoreDoc[] result = hits.scoreDocs;
     assertEquals(expectedResult.length(),hits.totalHits);
     StringBuilder buff = new StringBuilder(10);
@@ -1197,4 +1194,23 @@ public class TestSort extends LuceneTestCase implements Serializable {
     indexStore.close();
   }
 
+  public void testCountingCollector() throws Exception {
+    Directory indexStore = newDirectory();
+    RandomIndexWriter writer = new RandomIndexWriter(random, indexStore);
+    for (int i=0; i<5; i++) {
+      Document doc = new Document();
+      doc.add (new Field ("string", "a"+i, Field.Store.NO, Field.Index.NOT_ANALYZED));
+      doc.add (new Field ("string", "b"+i, Field.Store.NO, Field.Index.NOT_ANALYZED));
+      writer.addDocument (doc);
+    }
+    IndexReader reader = writer.getReader();
+    writer.close();
+
+    IndexSearcher searcher = new IndexSearcher(reader);
+    TotalHitCountCollector c = new TotalHitCountCollector();
+    searcher.search(new MatchAllDocsQuery(), null, c);
+    assertEquals(5, c.getTotalHits());
+    reader.close();
+    indexStore.close();
+  }
 }