/**
* 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.solr.search;
import org.apache.lucene.search.*;
/**
* Extra lucene sorting utilities & convenience methods
*
* @version $Id: Sorting.java 778893 2009-05-26 21:34:53Z yonik $
*
*/
public class Sorting {
/** Returns a {@link SortField} for a string field.
* If nullLast and nullFirst are both false, then default lucene string sorting is used where
* null strings sort first in an ascending sort, and last in a descending sort.
*
* @param fieldName the name of the field to sort on
* @param reverse true for a reverse (desc) sort
* @param nullLast true if null should come last, regardless of sort order
* @param nullFirst true if null should come first, regardless of sort order
* @return SortField
*/
public static SortField getStringSortField(String fieldName, boolean reverse, boolean nullLast, boolean nullFirst) {
if (nullLast) {
if (!reverse) return new SortField(fieldName, nullStringLastComparatorSource);
else return new SortField(fieldName, SortField.STRING, true);
} else if (nullFirst) {
if (reverse) return new SortField(fieldName, nullStringLastComparatorSource, true);
else return new SortField(fieldName, SortField.STRING, false);
} else {
return new SortField(fieldName, SortField.STRING, reverse);
}
}
static final FieldComparatorSource nullStringLastComparatorSource = new MissingStringLastComparatorSource(null);
}