/*
* 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.queries.function.valuesource;
import org.apache.lucene.index.*;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.similarities.PerFieldSimilarityWrapper;
import org.apache.lucene.search.similarities.Similarity;
import org.apache.lucene.search.similarities.TFIDFSimilarity;
import org.apache.lucene.util.BytesRef;
import java.io.IOException;
import java.util.Map;
/**
* Function that returns {@link TFIDFSimilarity #idf(long, long)}
* for every document.
* <p>
* Note that the configured Similarity for the field must be
* a subclass of {@link TFIDFSimilarity}
* @lucene.internal */
public class IDFValueSource extends DocFreqValueSource {
public IDFValueSource(String field, String val, String indexedField, BytesRef indexedBytes) {
super(field, val, indexedField, indexedBytes);
}
@Override
public String name() {
return "idf";
}
@Override
public FunctionValues getValues(Map context, AtomicReaderContext readerContext) throws IOException {
IndexSearcher searcher = (IndexSearcher)context.get("searcher");
TFIDFSimilarity sim = asTFIDF(searcher.getSimilarity(), field);
if (sim == null) {
throw new UnsupportedOperationException("requires a TFIDFSimilarity (such as DefaultSimilarity)");
}
int docfreq = searcher.getIndexReader().docFreq(new Term(indexedField, indexedBytes));
float idf = sim.idf(docfreq, searcher.getIndexReader().maxDoc());
return new ConstDoubleDocValues(idf, this);
}
// tries extra hard to cast the sim to TFIDFSimilarity
static TFIDFSimilarity asTFIDF(Similarity sim, String field) {
while (sim instanceof PerFieldSimilarityWrapper) {
sim = ((PerFieldSimilarityWrapper)sim).get(field);
}
if (sim instanceof TFIDFSimilarity) {
return (TFIDFSimilarity)sim;
} else {
return null;
}
}
}