| /* |
| * 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.highlight; |
| |
| import java.io.IOException; |
| import java.util.HashSet; |
| import java.util.Set; |
| import java.util.function.Predicate; |
| import org.apache.lucene.index.IndexReader; |
| import org.apache.lucene.index.MultiReader; |
| import org.apache.lucene.index.Term; |
| import org.apache.lucene.search.BooleanClause; |
| import org.apache.lucene.search.BoostQuery; |
| import org.apache.lucene.search.IndexSearcher; |
| import org.apache.lucene.search.Query; |
| import org.apache.lucene.search.QueryVisitor; |
| |
| /** |
| * Utility class used to extract the terms used in a query, plus any weights. This class will not |
| * find terms for MultiTermQuery, TermRangeQuery and PrefixQuery classes so the caller must pass a |
| * rewritten query (see Query.rewrite) to obtain a list of expanded terms. |
| */ |
| public final class QueryTermExtractor { |
| |
| /** for term extraction */ |
| private static final IndexSearcher EMPTY_INDEXSEARCHER; |
| |
| static { |
| try { |
| IndexReader emptyReader = new MultiReader(); |
| EMPTY_INDEXSEARCHER = new IndexSearcher(emptyReader); |
| EMPTY_INDEXSEARCHER.setQueryCache(null); |
| } catch (IOException bogus) { |
| throw new RuntimeException(bogus); |
| } |
| } |
| |
| /** |
| * Extracts all terms texts of a given Query into an array of WeightedTerms |
| * |
| * @param query Query to extract term texts from |
| * @return an array of the terms used in a query, plus their weights. |
| */ |
| public static final WeightedTerm[] getTerms(Query query) { |
| return getTerms(query, false); |
| } |
| |
| /** |
| * Extracts all terms texts of a given Query into an array of WeightedTerms |
| * |
| * @param query Query to extract term texts from |
| * @param reader used to compute IDF which can be used to a) score selected fragments better b) |
| * use graded highlights eg changing intensity of font color |
| * @param fieldName the field on which Inverse Document Frequency (IDF) calculations are based |
| * @return an array of the terms used in a query, plus their weights. |
| */ |
| public static final WeightedTerm[] getIdfWeightedTerms( |
| Query query, IndexReader reader, String fieldName) { |
| WeightedTerm[] terms = getTerms(query, false, fieldName); |
| int totalNumDocs = reader.maxDoc(); |
| for (int i = 0; i < terms.length; i++) { |
| try { |
| int docFreq = reader.docFreq(new Term(fieldName, terms[i].term)); |
| // IDF algorithm taken from ClassicSimilarity class |
| float idf = (float) (Math.log(totalNumDocs / (double) (docFreq + 1)) + 1.0); |
| terms[i].weight *= idf; |
| } catch (IOException e) { |
| // ignore |
| } |
| } |
| return terms; |
| } |
| |
| /** |
| * Extracts all terms texts of a given Query into an array of WeightedTerms |
| * |
| * @param query Query to extract term texts from |
| * @param prohibited <code>true</code> to extract "prohibited" terms, too |
| * @param fieldName The fieldName used to filter query terms |
| * @return an array of the terms used in a query, plus their weights. |
| */ |
| public static WeightedTerm[] getTerms(Query query, boolean prohibited, String fieldName) { |
| HashSet<WeightedTerm> terms = new HashSet<>(); |
| Predicate<String> fieldSelector = fieldName == null ? f -> true : fieldName::equals; |
| query.visit(new BoostedTermExtractor(1, terms, prohibited, fieldSelector)); |
| return terms.toArray(new WeightedTerm[0]); |
| } |
| |
| /** |
| * Extracts all terms texts of a given Query into an array of WeightedTerms |
| * |
| * @param query Query to extract term texts from |
| * @param prohibited <code>true</code> to extract "prohibited" terms, too |
| * @return an array of the terms used in a query, plus their weights. |
| */ |
| public static final WeightedTerm[] getTerms(Query query, boolean prohibited) { |
| return getTerms(query, prohibited, null); |
| } |
| |
| private static class BoostedTermExtractor extends QueryVisitor { |
| |
| final float boost; |
| final Set<WeightedTerm> terms; |
| final boolean includeProhibited; |
| final Predicate<String> fieldSelector; |
| |
| private BoostedTermExtractor( |
| float boost, |
| Set<WeightedTerm> terms, |
| boolean includeProhibited, |
| Predicate<String> fieldSelector) { |
| this.boost = boost; |
| this.terms = terms; |
| this.includeProhibited = includeProhibited; |
| this.fieldSelector = fieldSelector; |
| } |
| |
| @Override |
| public boolean acceptField(String field) { |
| return fieldSelector.test(field); |
| } |
| |
| @Override |
| public void consumeTerms(Query query, Term... terms) { |
| for (Term term : terms) { |
| this.terms.add(new WeightedTerm(boost, term.text())); |
| } |
| } |
| |
| @Override |
| public QueryVisitor getSubVisitor(BooleanClause.Occur occur, Query parent) { |
| if (parent instanceof BoostQuery) { |
| float newboost = boost * ((BoostQuery) parent).getBoost(); |
| return new BoostedTermExtractor(newboost, terms, includeProhibited, fieldSelector); |
| } |
| if (occur == BooleanClause.Occur.MUST_NOT && includeProhibited == false) { |
| return QueryVisitor.EMPTY_VISITOR; |
| } |
| return this; |
| } |
| } |
| } |