/*
* 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
*
*
*
*/
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) {
SortField sortField = new SortField(fieldName, SortField.Type.STRING, reverse);
applyMissingFirstLast(sortField, reverse, nullLast, nullFirst);
return sortField;
}
/** Like {@link #getStringSortField}) except safe for tokenized fields */
public static SortField getTextSortField(String fieldName, boolean reverse, boolean nullLast, boolean nullFirst) {
SortField sortField = new SortedSetSortField(fieldName, reverse);
applyMissingFirstLast(sortField, reverse, nullLast, nullFirst);
return sortField;
}
private static void applyMissingFirstLast(SortField in, boolean reverse, boolean nullLast, boolean nullFirst) {
if (nullFirst && nullLast) {
throw new IllegalArgumentException("Cannot specify missing values as both first and last");
}
// 4 cases:
// missingFirst / forward: default lucene behavior
// missingFirst / reverse: set sortMissingLast
// missingLast / forward: set sortMissingLast
// missingLast / reverse: default lucene behavior
if (nullFirst && reverse) {
in.setMissingValue(SortField.STRING_LAST);
} else if (nullLast && !reverse) {
in.setMissingValue(SortField.STRING_LAST);
}
}
}