| 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> { |
| |
| /** |
| * 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 class="prettyprint"> |
| * PriorityQueue<ScoreDoc> 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 > 0; i--) pq.pop(); |
| * |
| * // Now pop the truly added elements. |
| * ScoreDoc[] results = new ScoreDoc[totalHits]; |
| * for (int i = totalHits - 1; i >= 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) { |
| super(size, prePopulate); |
| } |
| |
| @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 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; |
| } |
| } |