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.
 */

/** Lower-level search API.
 * <br>HitCollectors are primarily meant to be used to implement queries,
 * sorting and filtering.
 * @see Searcher#search(Query,HitCollector)
 * @version $Id: HitCollector.java 472959 2006-11-09 16:21:50Z yonik $
 */
public abstract class HitCollector {
  /** Called once for every non-zero scoring document, with the document number
   * and its score.
   *
   * <P>If, for example, an application wished to collect all of the hits for a
   * query in a BitSet, then it might:<pre>
   *   Searcher searcher = new IndexSearcher(indexReader);
   *   final BitSet bits = new BitSet(indexReader.maxDoc());
   *   searcher.search(query, new HitCollector() {
   *       public void collect(int doc, float score) {
   *         bits.set(doc);
   *       }
   *     });
   * </pre>
   *
   * <p>Note: This is called in an inner search loop.  For good search
   * performance, implementations of this method should not call
   * {@link Searcher#doc(int)} or
   * {@link org.apache.lucene.index.IndexReader#document(int)} on every
   * document number encountered.  Doing so can slow searches by an order
   * of magnitude or more.
   * <p>Note: The <code>score</code> passed to this method is a raw score.
   * In other words, the score will not necessarily be a float whose value is
   * between 0 and 1.
   */
  public abstract void collect(int doc, float score);
}