beagled/Lucene.Net/Search/Weight.cs

   1 /*
   2  * Copyright 2004 The Apache Software Foundation
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 using System;
  17 using IndexReader = Lucene.Net.Index.IndexReader;
  18 namespace Lucene.Net.Search
  19 {
  20
  21     /// <summary>Expert: Calculate query weights and build query scorers.
  22     /// <p>
  23     /// The purpose of Weight is to make it so that searching does not modify
  24     /// a Query, so that a Query instance can be reused. <br>
  25     /// Searcher dependent state of the query should reside in the Weight. <br>
  26     /// IndexReader dependent state should reside in the Scorer.
  27     /// <p>
  28     /// A <code>Weight</code> is used in the following way:
  29     /// <ol>
  30     /// <li>A <code>Weight</code> is constructed by a top-level query,
  31     /// given a <code>Searcher</code> ({@link Query#CreateWeight(Searcher)}).
  32     /// <li>The {@link #SumOfSquaredWeights()} method is called
  33     /// on the <code>Weight</code> to compute
  34     /// the query normalization factor {@link Similarity#QueryNorm(float)}
  35     /// of the query clauses contained in the query.
  36     /// <li>The query normalization factor is passed to {@link #normalize(float)}.
  37     /// At this point the weighting is complete.
  38     /// <li>A <code>Scorer</code> is constructed by {@link #Scorer(IndexReader)}.
  39     /// </ol>
  40     /// </summary>
  41     public interface Weight
  42         {
  43         /// <summary>The query that this concerns. </summary>
  44         Query GetQuery();
  45
  46         /// <summary>The weight for this query. </summary>
  47         float GetValue();
  48
  49                 /// <summary>The sum of squared weights of contained query clauses. </summary>
  50                 float SumOfSquaredWeights();
  51
  52                 /// <summary>Assigns the query normalization factor to this. </summary>
  53                 void  Normalize(float norm);
  54
  55                 /// <summary>Constructs a scorer for this. </summary>
  56                 Scorer Scorer(IndexReader reader);
  57
  58                 /// <summary>An explanation of the score computation for the named document. </summary>
  59                 Explanation Explain(IndexReader reader, int doc);
  60         }
  61 }