| /* |
| * 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.AtomicReader; |
| import org.apache.lucene.index.AtomicReaderContext; |
| import org.apache.lucene.index.CompositeReader; |
| import org.apache.lucene.index.IndexReader; |
| import org.apache.lucene.index.ReaderUtil; |
| import org.apache.lucene.index.SlowCompositeReaderWrapper; |
| import org.apache.lucene.index.SortedDocValues; |
| import org.apache.lucene.queries.function.FunctionValues; |
| import org.apache.lucene.queries.function.ValueSource; |
| import org.apache.lucene.queries.function.docvalues.IntDocValues; |
| import org.apache.lucene.search.FieldCache; |
| |
| /** |
| * Obtains the ordinal of the field value from the default Lucene {@link org.apache.lucene.search.FieldCache} using getTermsIndex() |
| * and reverses the order. |
| * <br> |
| * The native lucene index order is used to assign an ordinal value for each field value. |
| * <br>Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1. |
| * <br> |
| * Example of reverse ordinal (rord):<br> |
| * If there were only three field values: "apple","banana","pear" |
| * <br>then rord("apple")=3, rord("banana")=2, ord("pear")=1 |
| * <p> |
| * WARNING: ord() depends on the position in an index and can thus change when other documents are inserted or deleted, |
| * or if a MultiSearcher is used. |
| * <br> |
| * WARNING: as of Solr 1.4, ord() and rord() can cause excess memory use since they must use a FieldCache entry |
| * at the top level reader, while sorting and function queries now use entries at the segment level. Hence sorting |
| * or using a different function query, in addition to ord()/rord() will double memory use. |
| * |
| * |
| */ |
| |
| public class ReverseOrdFieldSource extends ValueSource { |
| public final String field; |
| |
| public ReverseOrdFieldSource(String field) { |
| this.field = field; |
| } |
| |
| @Override |
| public String description() { |
| return "rord("+field+')'; |
| } |
| |
| // TODO: this is trappy? perhaps this query instead should make you pass a slow reader yourself? |
| @Override |
| public FunctionValues getValues(Map context, AtomicReaderContext readerContext) throws IOException { |
| final IndexReader topReader = ReaderUtil.getTopLevelContext(readerContext).reader(); |
| final AtomicReader r = SlowCompositeReaderWrapper.wrap(topReader); |
| final int off = readerContext.docBase; |
| |
| final SortedDocValues sindex = FieldCache.DEFAULT.getTermsIndex(r, field); |
| final int end = sindex.getValueCount(); |
| |
| return new IntDocValues(this) { |
| @Override |
| public int intVal(int doc) { |
| return (end - sindex.getOrd(doc+off) - 1); |
| } |
| }; |
| } |
| |
| @Override |
| public boolean equals(Object o) { |
| if (o == null || (o.getClass() != ReverseOrdFieldSource.class)) return false; |
| ReverseOrdFieldSource other = (ReverseOrdFieldSource)o; |
| return this.field.equals(other.field); |
| } |
| |
| private static final int hcode = ReverseOrdFieldSource.class.hashCode(); |
| @Override |
| public int hashCode() { |
| return hcode + field.hashCode(); |
| } |
| |
| } |