| /* |
| * 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.luke.models.overview; |
| |
| import java.util.Arrays; |
| import java.util.Collections; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Objects; |
| import java.util.WeakHashMap; |
| import java.util.stream.Collectors; |
| |
| import org.apache.lucene.index.IndexReader; |
| import org.apache.lucene.misc.HighFreqTerms; |
| |
| /** |
| * An utility class that collects terms and their statistics in a specific field. |
| */ |
| final class TopTerms { |
| |
| private final IndexReader reader; |
| |
| private final Map<String, List<TermStats>> topTermsCache; |
| |
| TopTerms(IndexReader reader) { |
| this.reader = Objects.requireNonNull(reader); |
| this.topTermsCache = new WeakHashMap<>(); |
| } |
| |
| /** |
| * Returns the top indexed terms with their statistics for the specified field. |
| * |
| * @param field - the field name |
| * @param numTerms - the max number of terms to be returned |
| * @throws Exception - if an error occurs when collecting term statistics |
| */ |
| List<TermStats> getTopTerms(String field, int numTerms) throws Exception { |
| |
| if (!topTermsCache.containsKey(field) || topTermsCache.get(field).size() < numTerms) { |
| org.apache.lucene.misc.TermStats[] stats = |
| HighFreqTerms.getHighFreqTerms(reader, numTerms, field, new HighFreqTerms.DocFreqComparator()); |
| |
| List<TermStats> topTerms = Arrays.stream(stats) |
| .map(TermStats::of) |
| .collect(Collectors.toList()); |
| |
| // cache computed statistics for later uses |
| topTermsCache.put(field, topTerms); |
| } |
| |
| return Collections.unmodifiableList(topTermsCache.get(field)); |
| } |
| } |