| /* |
| * 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, 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; |
| } |
| } |
| } |
| |