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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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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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 TFIDFSimilarity.idf(long, long) for every document.

Note that the configured Similarity for the field must be a subclass of TFIDFSimilarity

@lucene.internal
/** * 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, LeafReaderContext 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 ClassicSimilarity)"); } int docfreq = searcher.getIndexReader().docFreq(new Term(indexedField, indexedBytes)); float idf = sim.idf(docfreq, searcher.getIndexReader().maxDoc()); return new DocFreqValueSource.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; } } }