org.apache.lucene.search.ConstantScoreWeight.java Source code

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Here is the source code for org.apache.lucene.search.ConstantScoreWeight.java

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/*
 * 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.
 */
package org.apache.lucene.search;

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

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.index.Term;

/**
 * A Weight that has a constant score equal to the boost of the wrapped query.
 * This is typically useful when building queries which do not produce
 * meaningful scores and are mostly useful for filtering.
 *
 * @lucene.internal
 */
public abstract class ConstantScoreWeight extends Weight {

    private final float score;

    protected ConstantScoreWeight(Query query, float score) {
        super(query);
        this.score = score;
    }

    @Override
    public void extractTerms(Set<Term> terms) {
        // most constant-score queries don't wrap index terms
        // eg. geo filters, doc values queries, ...
        // override if your constant-score query does wrap terms
    }

    /** Return the score produced by this {@link Weight}. */
    protected final float score() {
        return score;
    }

    @Override
    public Explanation explain(LeafReaderContext context, int doc) throws IOException {
        final Scorer s = scorer(context);
        final boolean exists;
        if (s == null) {
            exists = false;
        } else {
            final TwoPhaseIterator twoPhase = s.twoPhaseIterator();
            if (twoPhase == null) {
                exists = s.iterator().advance(doc) == doc;
            } else {
                exists = twoPhase.approximation().advance(doc) == doc && twoPhase.matches();
            }
        }

        if (exists) {
            return Explanation.match(score, getQuery().toString() + (score == 1f ? "" : "^" + score));
        } else {
            return Explanation.noMatch(getQuery().toString() + " doesn't match id " + doc);
        }
    }

}