BoostScoreFunction.java

/*
 * Licensed to ElasticSearch and Shay Banon under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. ElasticSearch 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.elasticsearch.common.lucene.search.function;

import org.apache.lucene.index.IndexReader;
import org.apache.lucene.search.Explanation;

/**
 *
 */
public class BoostScoreFunction implements ScoreFunction {

    private final float boost;

    public BoostScoreFunction(float boost) {
        this.boost = boost;
    }


    public float getBoost() {
        return boost;
    }

    @Override
    public void setNextReader(IndexReader reader) {
        // nothing to do here...
    }

    @Override
    public float score(int docId, float subQueryScore) {
        return subQueryScore * boost;
    }

    @Override
    public float factor(int docId) {
        return boost;
    }

    @Override
    public Explanation explainScore(int docId, Explanation subQueryExpl) {
        Explanation exp = new Explanation(boost * subQueryExpl.getValue(), "static boost function: product of:");
        exp.addDetail(subQueryExpl);
        exp.addDetail(new Explanation(boost, "boostFactor"));
        return exp;
    }

    @Override
    public Explanation explainFactor(int docId) {
        return new Explanation(boost, "boostFactor");
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        BoostScoreFunction that = (BoostScoreFunction) o;

        if (Float.compare(that.boost, boost) != 0) return false;

        return true;
    }

    @Override
    public int hashCode() {
        return (boost != +0.0f ? Float.floatToIntBits(boost) : 0);
    }

    @Override
    public String toString() {
        return "boost[" + boost + "]";
    }
}