Lucene example source code file (ValueSourceQuery.java)

This example Lucene source code file (ValueSourceQuery.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Lucene tags/keywords

docvalues, explanation, explanation, io, ioexception, ioexception, no_more_docs, override, override, query, scorer, util, valuesourcequery, valuesourcequery, valuesourcescorer, valuesourceweight

The Lucene ValueSourceQuery.java source code

package org.apache.lucene.search.function;

/**
 * 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.
 */

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.index.Term;
import org.apache.lucene.index.TermDocs;
import org.apache.lucene.search.*;
import org.apache.lucene.util.ToStringUtils;

import java.io.IOException;
import java.util.Set;

/**
 * Expert: A Query that sets the scores of document to the
 * values obtained from a {@link org.apache.lucene.search.function.ValueSource ValueSource}.
 * <p>
 * This query provides a score for <em>each and every undeleted document in the index.    
 * <p>
 * The value source can be based on a (cached) value of an indexed field, but it
 * can also be based on an external source, e.g. values read from an external database. 
 * <p>
 * Score is set as: Score(doc,query) = query.getBoost()<sup>2 * valueSource(doc).  
 *
 * @lucene.experimental
 */
public class ValueSourceQuery extends Query {
  ValueSource valSrc;

  /**
   * Create a value source query
   * @param valSrc provides the values defines the function to be used for scoring
   */
  public ValueSourceQuery(ValueSource valSrc) {
    this.valSrc=valSrc;
  }

  /*(non-Javadoc) @see org.apache.lucene.search.Query#rewrite(org.apache.lucene.index.IndexReader) */
  @Override
  public Query rewrite(IndexReader reader) throws IOException {
    return this;
  }

  /*(non-Javadoc) @see org.apache.lucene.search.Query#extractTerms(java.util.Set) */
  @Override
  public void extractTerms(Set<Term> terms) {
    // no terms involved here
  }

  class ValueSourceWeight extends Weight {
    Similarity similarity;
    float queryNorm;
    float queryWeight;

    public ValueSourceWeight(Searcher searcher) {
      this.similarity = getSimilarity(searcher);
    }

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

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

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#sumOfSquaredWeights() */
    @Override
    public float sumOfSquaredWeights() throws IOException {
      queryWeight = getBoost();
      return queryWeight * queryWeight;
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#normalize(float) */
    @Override
    public void normalize(float norm) {
      this.queryNorm = norm;
      queryWeight *= this.queryNorm;
    }

    @Override
    public Scorer scorer(IndexReader reader, boolean scoreDocsInOrder, boolean topScorer) throws IOException {
      return new ValueSourceScorer(similarity, reader, this);
    }

    /*(non-Javadoc) @see org.apache.lucene.search.Weight#explain(org.apache.lucene.index.IndexReader, int) */
    @Override
    public Explanation explain(IndexReader reader, int doc) throws IOException {
      DocValues vals = valSrc.getValues(reader);
      float sc = queryWeight * vals.floatVal(doc);

      Explanation result = new ComplexExplanation(
        true, sc, ValueSourceQuery.this.toString() + ", product of:");

      result.addDetail(vals.explain(doc));
      result.addDetail(new Explanation(getBoost(), "boost"));
      result.addDetail(new Explanation(queryNorm,"queryNorm"));
      return result;
    }
  }

  /**
   * A scorer that (simply) matches all documents, and scores each document with 
   * the value of the value source in effect. As an example, if the value source 
   * is a (cached) field source, then value of that field in that document will 
   * be used. (assuming field is indexed for this doc, with a single token.)   
   */
  private class ValueSourceScorer extends Scorer {
    private final float qWeight;
    private final DocValues vals;
    private final TermDocs termDocs;
    private int doc = -1;

    // constructor
    private ValueSourceScorer(Similarity similarity, IndexReader reader, ValueSourceWeight w) throws IOException {
      super(similarity,w);
      qWeight = w.getValue();
      // this is when/where the values are first created.
      vals = valSrc.getValues(reader);
      termDocs = reader.termDocs(null);
    }

    @Override
    public int nextDoc() throws IOException {
      return doc = termDocs.next() ? termDocs.doc() : NO_MORE_DOCS;
    }
    
    @Override
    public int docID() {
      return doc;
    }
    
    @Override
    public int advance(int target) throws IOException {
      return doc = termDocs.skipTo(target) ? termDocs.doc() : NO_MORE_DOCS;
    }
    
    /*(non-Javadoc) @see org.apache.lucene.search.Scorer#score() */
    @Override
    public float score() throws IOException {
      return qWeight * vals.floatVal(termDocs.doc());
    }
  }

  @Override
  public Weight createWeight(Searcher searcher) {
    return new ValueSourceQuery.ValueSourceWeight(searcher);
  }

  @Override
  public String toString(String field) {
    return valSrc.toString() + ToStringUtils.boost(getBoost());
  }

  /** Returns true if <code>o is equal to this. */
  @Override
  public boolean equals(Object o) {
    if (this == o)
      return true;
    if (!super.equals(o))
      return false;
    if (getClass() != o.getClass()) {
      return false;
    }
    ValueSourceQuery other = (ValueSourceQuery)o;
    return this.getBoost() == other.getBoost()
           && this.valSrc.equals(other.valSrc);
  }

  /** Returns a hash code value for this object. */
  @Override
  public int hashCode() {
    return (getClass().hashCode() + valSrc.hashCode()) ^ Float.floatToIntBits(getBoost());
  }

}