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Diffstat (limited to 'src/core/Search/HitQueue.cs')
| -rw-r--r-- | src/core/Search/HitQueue.cs | 95 |
1 files changed, 95 insertions, 0 deletions
diff --git a/src/core/Search/HitQueue.cs b/src/core/Search/HitQueue.cs new file mode 100644 index 0000000..925d3a6 --- /dev/null +++ b/src/core/Search/HitQueue.cs @@ -0,0 +1,95 @@ +/* + * 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. + */ + +using System; +using Lucene.Net.Util; + +namespace Lucene.Net.Search +{ + + public sealed class HitQueue : PriorityQueue<ScoreDoc> + { + + private bool prePopulate; + + /// <summary> Creates a new instance with <c>size</c> elements. If + /// <c>prePopulate</c> is set to true, the queue will pre-populate itself + /// with sentinel objects and set its <see cref="PriorityQueue{T}.Size()" /> to <c>size</c>. In + /// that case, you should not rely on <see cref="PriorityQueue{T}.Size()" /> to get the number of + /// actual elements that were added to the queue, but keep track yourself.<br/> + /// <b>NOTE:</b> in case <c>prePopulate</c> is true, you should pop + /// elements from the queue using the following code example: + /// + /// <code> + /// 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 > 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(); + /// } + /// </code> + /// + /// <p/><b>NOTE</b>: This class pre-allocate a full array of + /// length <c>size</c>. + /// + /// </summary> + /// <param name="size">the requested size of this queue. + /// </param> + /// <param name="prePopulate">specifies whether to pre-populate the queue with sentinel values. + /// </param> + /// <seealso cref="SentinelObject"> + /// </seealso> + public /*internal*/ HitQueue(int size, bool prePopulate) + { + this.prePopulate = prePopulate; + Initialize(size); + } + + // Returns null if prePopulate is false. + + protected internal override ScoreDoc SentinelObject + { + get + { + // 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(System.Int32.MaxValue, System.Single.NegativeInfinity); + } + } + + public override bool LessThan(ScoreDoc hitA, ScoreDoc hitB) + { + if (hitA.Score == hitB.Score) + return hitA.Doc > hitB.Doc; + else + return hitA.Score < hitB.Score; + } + } +}
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