pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / search / HitQueue.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/HitQueue.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/HitQueue.java
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+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.util.PriorityQueue;
+
+final class HitQueue extends PriorityQueue<ScoreDoc> {
+
+  private boolean prePopulate;
+
+  /**
+   * Creates a new instance with <code>size</code> elements. If
+   * <code>prePopulate</code> is set to true, the queue will pre-populate itself
+   * with sentinel objects and set its {@link #size()} to <code>size</code>. In
+   * that case, you should not rely on {@link #size()} to get the number of
+   * actual elements that were added to the queue, but keep track yourself.<br>
+   * <b>NOTE:</b> in case <code>prePopulate</code> is true, you should pop
+   * elements from the queue using the following code example:
+   * 
+   * <pre>
+   * PriorityQueue pq = new HitQueue(10, true); // pre-populate.
+   * ScoreDoc top = pq.top();
+   * 
+   * // Add/Update one element.
+   * top.score = 1.0f;
+   * top.doc = 0;
+   * top = (ScoreDoc) pq.updateTop();
+   * int totalHits = 1;
+   * 
+   * // Now pop only the elements that were *truly* inserted.
+   * // First, pop all the sentinel elements (there are pq.size() - totalHits).
+   * for (int i = pq.size() - totalHits; i &gt; 0; i--) pq.pop();
+   * 
+   * // Now pop the truly added elements.
+   * ScoreDoc[] results = new ScoreDoc[totalHits];
+   * for (int i = totalHits - 1; i &gt;= 0; i--) {
+   *   results[i] = (ScoreDoc) pq.pop();
+   * }
+   * </pre>
+   * 
+   * <p><b>NOTE</b>: This class pre-allocate a full array of
+   * length <code>size</code>.
+   * 
+   * @param size
+   *          the requested size of this queue.
+   * @param prePopulate
+   *          specifies whether to pre-populate the queue with sentinel values.
+   * @see #getSentinelObject()
+   */
+  HitQueue(int size, boolean prePopulate) {
+    this.prePopulate = prePopulate;
+    initialize(size);
+  }
+
+  // Returns null if prePopulate is false.
+  @Override
+  protected ScoreDoc getSentinelObject() {
+    // Always set the doc Id to MAX_VALUE so that it won't be favored by
+    // lessThan. This generally should not happen since if score is not NEG_INF,
+    // TopScoreDocCollector will always add the object to the queue.
+    return !prePopulate ? null : new ScoreDoc(Integer.MAX_VALUE, Float.NEGATIVE_INFINITY);
+  }
+  
+  @Override
+  protected final boolean lessThan(ScoreDoc hitA, ScoreDoc hitB) {
+    if (hitA.score == hitB.score)
+      return hitA.doc > hitB.doc; 
+    else
+      return hitA.score < hitB.score;
+  }
+}