/*
* 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.similarities;
import java.io.IOException;
import org.apache.lucene.index.FieldInvertState;
import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.search.CollectionStatistics;
import org.apache.lucene.search.Explanation;
import org.apache.lucene.search.TermStatistics;
import org.apache.lucene.util.BytesRef;
/**
* Simple similarity that gives terms a score that is equal to their query
* boost. This similarity is typically used with disabled norms since neither
* document statistics nor index statistics are used for scoring. That said,
* if norms are enabled, they will be computed the same way as
* {@link SimilarityBase} and {@link BM25Similarity} with
* {@link SimilarityBase#setDiscountOverlaps(boolean) discounted overlaps}
* so that the {@link Similarity} can be changed after the index has been
* created.
*/
public class BooleanSimilarity extends Similarity {
private static final Similarity BM25_SIM = new BM25Similarity();
/** Sole constructor */
public BooleanSimilarity() {}
@Override
public long computeNorm(FieldInvertState state) {
return BM25_SIM.computeNorm(state);
}
@Override
public SimWeight computeWeight(float boost, CollectionStatistics collectionStats, TermStatistics... termStats) {
return new BooleanWeight(boost);
}
private static class BooleanWeight extends SimWeight {
final float boost;
BooleanWeight(float boost) {
this.boost = boost;
}
}
@Override
public SimScorer simScorer(SimWeight weight, LeafReaderContext context) throws IOException {
final float boost = ((BooleanWeight) weight).boost;
return new SimScorer() {
@Override
public float score(int doc, float freq) throws IOException {
return boost;
}
@Override
public Explanation explain(int doc, Explanation freq) throws IOException {
Explanation queryBoostExpl = Explanation.match(boost, "query boost");
return Explanation.match(
queryBoostExpl.getValue(),
"score(" + getClass().getSimpleName() + ", doc=" + doc + "), computed from:",
queryBoostExpl);
}
@Override
public float computeSlopFactor(int distance) {
return 1f;
}
@Override
public float computePayloadFactor(int doc, int start, int end, BytesRef payload) {
return 1f;
}
};
}
}