src/Lucene.Net/Search/TopDocCollector.cs

/*
 * 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 PriorityQueue = Lucene.Net.Util.PriorityQueue;

namespace Lucene.Net.Search
{
	
	/// <summary>A {@link HitCollector} implementation that collects the top-scoring
	/// documents, returning them as a {@link TopDocs}.  This is used by {@link
	/// IndexSearcher} to implement {@link TopDocs}-based search.
	/// 
	/// <p>This may be extended, overriding the collect method to, e.g.,
	/// conditionally invoke <code>super()</code> in order to filter which
	/// documents are collected.
	/// 
	/// </summary>
	public class TopDocCollector : HitCollector
	{
		
		private ScoreDoc reusableSD;
		
		internal int totalHits;
		internal PriorityQueue hq;
		
		/// <summary>Construct to collect a given number of hits.</summary>
		/// <param name="numHits">the maximum number of hits to collect
		/// </param>
		public TopDocCollector(int numHits) : this(numHits, new HitQueue(numHits))
		{
		}
		
		internal TopDocCollector(int numHits, PriorityQueue hq)
		{
			this.hq = hq;
		}
		
		// javadoc inherited
		public override void  Collect(int doc, float score)
		{
			if (score > 0.0f)
			{
				totalHits++;
				if (reusableSD == null)
				{
					reusableSD = new ScoreDoc(doc, score);
				}
				else if (score >= reusableSD.score)
				{
					// reusableSD holds the last "rejected" entry, so, if
					// this new score is not better than that, there's no
					// need to try inserting it
					reusableSD.doc = doc;
					reusableSD.score = score;
				}
				else
				{
					return ;
				}
				reusableSD = (ScoreDoc) hq.InsertWithOverflow(reusableSD);
			}
		}
		
		/// <summary>The total number of documents that matched this query. </summary>
		public virtual int GetTotalHits()
		{
			return totalHits;
		}
		
		/// <summary>The top-scoring hits. </summary>
		public virtual TopDocs TopDocs()
		{
			ScoreDoc[] scoreDocs = new ScoreDoc[hq.Size()];
			for (int i = hq.Size() - 1; i >= 0; i--)
				// put docs in array
				scoreDocs[i] = (ScoreDoc) hq.Pop();
			
			float maxScore = (totalHits == 0) ? System.Single.NegativeInfinity : scoreDocs[0].score;
			
			return new TopDocs(totalHits, scoreDocs, maxScore);
		}
	}
}