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Apache Solr (module: core)
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/*
 * 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.
 */
package org.apache.solr.search;

import org.apache.lucene.search.TotalHits;

/**
 * DocList represents the result of a query: an ordered list of document ids with
 * optional score. This list contains a subset of the complete list of documents actually matched:
 * size() document ids starting at offset().
 *
 * @since solr 0.9
 */
public interface DocList {

  /**
   * Returns the zero based offset of this list within the total ordered list of matches to the
   * query.
   */
  public int offset();

  /** Returns the number of ids in this list. */
  public int size();

  /**
   * Returns the total number of matches for the search (as opposed to just the number collected
   * according to offset() and size()). Hence it's always true that
   * matches() >= size()
   *
   * @return number of matches for the search(query & any filters)
   */
  public long matches();

  public TotalHits.Relation hitCountRelation();

  /*
  public int getDoc(int pos);
  */

  // hmmm, what if a different slice could be generated from an existing DocSet
  // (and was before)...

  // how to distinguish cached values from logical values?
  // docSet could represent docs 10-20, but actually contain 0-100
  // should the big slice be cached independently, and a new class called
  // DocListSubset be created to refer to a range within the DocList?

  /** Get a subset of an existing DocList. Returns null if not possible. */
  public DocList subset(int offset, int len);

  /**
   * Returns an iterator that may be used to iterate over the documents in this DocList
   *
   * The order of the documents returned by this iterator is based on the Sort order of the
   * search that produced it. The Scoring information is meaningful only if hasScores()
   * returns true.
   *
   * @see #hasScores
   */
  public DocIterator iterator();

  /** True if scores were retained */
  public boolean hasScores();

  /**
   * The maximum score for the search... only valid if scores were retained (if hasScores()==true)
   */
  public float maxScore();
}