java/src/main/com/google/appengine/api/search/RescoringMatchScorer.java

   1 // Copyright 2012 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.search;
   4
   5 /**
   6  * Assigns a document score based on term frequency weighted on document parts.
   7  *
   8  * If you add a MatchScorer to a SortOptions as in the following code:
   9  * <pre>
  10  *  SortOptions sortOptions = SortOptions.newBuilder()
  11  *      .setMatchScorer(RescoringMatchScorer().newBuilder())
  12  *      .build();
  13  * </pre>
  14  * then this will sort the documents in descending score order. The scores will be
  15  * positive. If you want to sort in ascending order, then use the following code:
  16  * <pre>
  17  *   SortOptions sortOptions = SortOptions.newBuilder()
  18  *       .setMatchScorer(RescoringMatchScorer.newBuilder())
  19  *       .addSortExpression(
  20  *           SortExpression.newBuilder()
  21  *               .setExpression(SortExpression.SCORE_FIELD_NAME)
  22  *               .setDirection(SortExpression.SortDirection.ASCENDING)
  23  *               .setDefaultValueNumeric(0.0))
  24  *       .build();
  25  * </pre>
  26  * The scores in this case will be negative.
  27  *
  28  */
  29 public final class RescoringMatchScorer extends MatchScorer {
  30
  31   /**
  32    * A builder that constructs {@link RescoringMatchScorer RescoringMatchScorers}.
  33    * A RescoringMatchScorer will invoke a scorer on each search result. The
  34    * following code illustrates building a rescoring match scorer to score documents:
  35    * <p>
  36    * <pre>
  37    *   RescoringMatchScorer scorer = RescoringMatchScorer.newBuilder().build();
  38    * </pre>
  39    */
  40   public static final class Builder extends MatchScorer.Builder {
  41
  42     private Builder() {
  43     }
  44
  45     /**
  46      * Builds a {@link RescoringMatchScorer} from the set values.
  47      *
  48      * @return a {@link RescoringMatchScorer} built from the set values
  49      */
  50     @Override
  51     public RescoringMatchScorer build() {
  52       return new RescoringMatchScorer(this);
  53     }
  54   }
  55
  56   /**
  57    * Constructs a text sort specification using the values from the
  58    * {@link Builder}.
  59    */
  60   private RescoringMatchScorer(Builder builder) {
  61     super(MatchScorer.newBuilder());
  62   }
  63
  64   /**
  65    * Copies the contents of the RescoringMatchScorer into a scorer
  66    * spec protocol buffer.
  67    *
  68    * @return the protocol buffer builder with the contents of the
  69    * RescoringMatchScorer scoring information
  70    */
  71   @Override
  72   SearchServicePb.ScorerSpec.Builder copyToScorerSpecProtocolBuffer() {
  73     SearchServicePb.ScorerSpec.Builder builder = SearchServicePb.ScorerSpec.newBuilder();
  74     builder.setScorer(SearchServicePb.ScorerSpec.Scorer.RESCORING_MATCH_SCORER);
  75     return builder;
  76   }
  77
  78   /**
  79    * Creates and returns a RescoringMatchScorer Builder.
  80    *
  81    * @return a new {@link RescoringMatchScorer.Builder}. Set the parameters for scorer
  82    * on the Builder, and use the {@link Builder#build()} method
  83    * to create a concrete instance of RescoringMatchScorer
  84    */
  85   public static Builder newBuilder() {
  86     return new Builder();
  87   }
  88
  89   @Override
  90   public String toString() {
  91     return "RescoringMatchScorer()";
  92   }
  93 }