/*
 * 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 java.io.IOException;
import java.util.Map;

import org.apache.lucene.index.LeafReaderContext;
import org.apache.lucene.queries.function.FunctionValues;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.queries.function.docvalues.FloatDocValues;
import org.apache.lucene.search.CollectionStatistics;
import org.apache.lucene.search.IndexSearcher;
import org.apache.lucene.search.LeafSimScorer;
import org.apache.lucene.search.TermStatistics;
import org.apache.lucene.search.similarities.TFIDFSimilarity;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.search.similarities.Similarity.SimScorer;

Function that returns the decoded norm for every document.

Note that the configured Similarity for the field must be a subclass of TFIDFSimilarity and the contribution of the TF needs to be 1 when the freq is 1 and the contribution of the IDF needs to be 1 when docFreq == docCount == 1.

@lucene.internal
/** * Function that returns the decoded norm for every document. * <p> * Note that the configured Similarity for the field must be * a subclass of {@link TFIDFSimilarity} and the contribution of * the TF needs to be 1 when the freq is 1 and the contribution * of the IDF needs to be 1 when docFreq == docCount == 1. * @lucene.internal */
public class NormValueSource extends ValueSource { protected final String field; public NormValueSource(String field) { this.field = field; } public String name() { return "norm"; } @Override public String description() { return name() + '(' + field + ')'; } @Override public void createWeight(Map context, IndexSearcher searcher) throws IOException { context.put("searcher",searcher); } @Override public FunctionValues getValues(Map context, LeafReaderContext readerContext) throws IOException { IndexSearcher searcher = (IndexSearcher)context.get("searcher"); final TFIDFSimilarity similarity = IDFValueSource.asTFIDF(searcher.getSimilarity(), field); if (similarity == null) { throw new UnsupportedOperationException("requires a TFIDFSimilarity (such as ClassicSimilarity)"); } // Only works if the contribution of the tf is 1 when the freq is 1 and contribution of the idf // is 1 when docCount == docFreq == 1 final SimScorer simScorer = similarity.scorer(1f, new CollectionStatistics(field, 1, 1, 1, 1), new TermStatistics(new BytesRef("bogus"), 1, 1)); final LeafSimScorer leafSimScorer = new LeafSimScorer(simScorer, readerContext.reader(), field, true); return new FloatDocValues(this) { int lastDocID = -1; @Override public float floatVal(int docID) throws IOException { if (docID < lastDocID) { throw new AssertionError("docs out of order: lastDocID=" + lastDocID + " docID=" + docID); } lastDocID = docID; return leafSimScorer.score(docID, 1f); } }; } @Override public boolean equals(Object o) { if (this.getClass() != o.getClass()) { return false; } return this.field.equals(((NormValueSource)o).field); } @Override public int hashCode() { return this.getClass().hashCode() + field.hashCode(); } }