customscorequery.java

Lucene a java open-source SearchEngine Framework

    if(valSrcExpls.length == 1) {
      return customExplain(doc, subQueryExpl, valSrcExpls[0]);
    }
    if (valSrcExpls.length == 0) {
      return subQueryExpl;
    }
    float valSrcScore = 1;
    for(int i = 0; i < valSrcExpls.length; i++) {
      valSrcScore *= valSrcExpls[i].getValue();
    }
    Explanation exp = new Explanation( valSrcScore * subQueryExpl.getValue(), "custom score: product of:");
    exp.addDetail(subQueryExpl);
    for(int i = 0; i < valSrcExpls.length; i++) {
      exp.addDetail(valSrcExpls[i]);
    }
    return exp;
  }

  /**
   * Explain the custom score.
   * Whenever overriding {@link #customScore(int, float, float)}, 
   * this method should also be overridden to provide the correct explanation
   * for the part of the custom scoring.
   *  
   * @param doc doc being explained.
   * @param subQueryExpl explanation for the sub-query part.
   * @param valSrcExpl explanation for the value source part.
   * @return an explanation for the custom score
   */
  public Explanation customExplain(int doc, Explanation subQueryExpl, Explanation valSrcExpl) {
    float valSrcScore = 1;
    if (valSrcExpl != null) {
      valSrcScore *= valSrcExpl.getValue();
    }
    Explanation exp = new Explanation( valSrcScore * subQueryExpl.getValue(), "custom score: product of:");
    exp.addDetail(subQueryExpl);
    exp.addDetail(valSrcExpl);
    return exp;
  }

  //=========================== W E I G H T ============================
  
  private class CustomWeight implements Weight {
    Similarity similarity;
    Weight subQueryWeight;
    Weight[] valSrcWeights;
    boolean qStrict;

    public CustomWeight(Searcher searcher) throws IOException {
      this.similarity = getSimilarity(searcher);
      this.subQueryWeight = subQuery.weight(searcher); 
      this.subQueryWeight = subQuery.weight(searcher);
      this.valSrcWeights = new Weight[valSrcQueries.length];
      for(int i = 0; i < valSrcQueries.length; i++) {
        this.valSrcWeights[i] = valSrcQueries[i].createWeight(searcher);
      }
      this.qStrict = strict;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#getQuery() */
    public Query getQuery() {
      return CustomScoreQuery.this;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#getValue() */
    public float getValue() {
      return getBoost();
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#sumOfSquaredWeights() */
    public float sumOfSquaredWeights() throws IOException {
      float sum = subQueryWeight.sumOfSquaredWeights();
      for(int i = 0; i < valSrcWeights.length; i++) {
        if (qStrict) {
          valSrcWeights[i].sumOfSquaredWeights(); // do not include ValueSource part in the query normalization
        } else {
          sum += valSrcWeights[i].sumOfSquaredWeights();
        }
      }
      sum *= getBoost() * getBoost(); // boost each sub-weight
      return sum ;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#normalize(float) */
    public void normalize(float norm) {
      norm *= getBoost(); // incorporate boost
      subQueryWeight.normalize(norm);
      for(int i = 0; i < valSrcWeights.length; i++) {
        if (qStrict) {
          valSrcWeights[i].normalize(1); // do not normalize the ValueSource part
        } else {
          valSrcWeights[i].normalize(norm);
        }
      }
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#scorer(org.apache.lucene.index.IndexReader) */
    public Scorer scorer(IndexReader reader) throws IOException {
      Scorer subQueryScorer = subQueryWeight.scorer(reader);
      Scorer[] valSrcScorers = new Scorer[valSrcWeights.length];
      for(int i = 0; i < valSrcScorers.length; i++) {
         valSrcScorers[i] = valSrcWeights[i].scorer(reader);
      }
      return new CustomScorer(similarity, reader, this, subQueryScorer, valSrcScorers);
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#explain(org.apache.lucene.index.IndexReader, int) */
    public Explanation explain(IndexReader reader, int doc) throws IOException {
      return scorer(reader).explain(doc);
    }
  }


  //=========================== S C O R E R ============================
  
  /**
   * A scorer that applies a (callback) function on scores of the subQuery.
   */
  private class CustomScorer extends Scorer {
    private final CustomWeight weight;
    private final float qWeight;
    private Scorer subQueryScorer;
    private Scorer[] valSrcScorers;
    private IndexReader reader;
    private float vScores[]; // reused in score() to avoid allocating this array for each doc 

    // constructor
    private CustomScorer(Similarity similarity, IndexReader reader, CustomWeight w,
        Scorer subQueryScorer, Scorer[] valSrcScorers) throws IOException {
      super(similarity);
      this.weight = w;
      this.qWeight = w.getValue();
      this.subQueryScorer = subQueryScorer;
      this.valSrcScorers = valSrcScorers;
      this.reader = reader;
      this.vScores = new float[valSrcScorers.length];
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#next() */
    public boolean next() throws IOException {
      boolean hasNext = subQueryScorer.next();
      if(hasNext) {
    	  for(int i = 0; i < valSrcScorers.length; i++) {
    	    valSrcScorers[i].skipTo(subQueryScorer.doc());  
    	  }
      }
      return hasNext;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#doc() */
    public int doc() {
      return subQueryScorer.doc();
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#score() */
    public float score() throws IOException {
      for(int i = 0; i < valSrcScorers.length; i++) {
    	  vScores[i] = valSrcScorers[i].score();
      }
      return qWeight * customScore(subQueryScorer.doc(), subQueryScorer.score(), vScores);
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#skipTo(int) */
    public boolean skipTo(int target) throws IOException {
      boolean hasNext = subQueryScorer.skipTo(target);
      if(hasNext) {
      	for(int i = 0; i < valSrcScorers.length; i++) {
      	  valSrcScorers[i].skipTo(subQueryScorer.doc());
      	}
      }
      return hasNext;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#explain(int) */
    public Explanation explain(int doc) throws IOException {
      Explanation subQueryExpl = weight.subQueryWeight.explain(reader,doc);
      if (!subQueryExpl.isMatch()) {
        return subQueryExpl;
      }
      // match
      Explanation[] valSrcExpls = new Explanation[valSrcScorers.length];
      for(int i = 0; i < valSrcScorers.length; i++) {
        valSrcExpls[i] = valSrcScorers[i].explain(doc);
      }
      Explanation customExp = customExplain(doc,subQueryExpl,valSrcExpls);
      float sc = qWeight * customExp.getValue();
      Explanation res = new ComplexExplanation(
        true, sc, CustomScoreQuery.this.toString() + ", product of:");
      res.addDetail(customExp);
      res.addDetail(new Explanation(qWeight, "queryBoost")); // actually using the q boost as q weight (== weight value)
      return res;
    }
  }

  /*(non-Javadoc) @see org.apache.lucene.search.Query#createWeight(org.apache.lucene.search.Searcher) */
  protected Weight createWeight(Searcher searcher) throws IOException {
    return new CustomWeight(searcher);
  }

  /**
   * Checks if this is strict custom scoring.
   * In strict custom scoring, the ValueSource part of does not participate in weight normalization.
   * This may be useful when one wants full control over how scores are modified, and does 
   * not care about normalizing by the ValueSource part.
   * One particular case where this is useful if for testing this query.   
   * <P>
   * Note: only has effect when the ValueSource part is not null.
   */
  public boolean isStrict() {
    return strict;
  }

  /**
   * Set the strict mode of this query. 
   * @param strict The strict mode to set.
   * @see #isStrict()
   */
  public void setStrict(boolean strict) {
    this.strict = strict;
  }

  /**
   * A short name of this query, used in {@link #toString(String)}.
   */
  public String name() {
    return "custom";
  }

}