/*
* 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 com.aliyun.odps.mapred.bridge.type;
import java.util.HashMap;
import java.util.Map;
import com.aliyun.odps.Column;
import com.aliyun.odps.mapred.conf.JobConf;
import com.aliyun.odps.mapred.conf.JobConf.SortOrder;
/**
* 可以指定排序列的RecordComparator。可以指定列排序方式ASC或者DESC,默认排序策略是自然序(ASC)。
*/
public class ColumnBasedRecordComparator extends NaturalRecordComparator {
int[] selIdxs;
SortOrder[] sortOrder;
/**
* ColumnBasedRecordComparator的构造方法,指定排序列的下标索引。例如指定排序列的下标索引为0,3,则比较时先用第0列比较,
* 第0列相同时使用第3列比较。
*
* @param selIdxs
* 排序列的下标索引
* @param schema
* 整个Record的行属性
*/
public ColumnBasedRecordComparator(int[] selIdxs, Column[] schema) {
super(schema);
this.selIdxs = selIdxs;
this.sortOrder = null;
}
/**
* ColumnBasedRecordComparator的构造方法,指定排序列的列名。例如指定排序列的下标索引为“word”,“count”,则比较时先用word列比较,
* word列相同时使用count列比较。
*
* @param selCols
* @param schema
*/
public ColumnBasedRecordComparator(String[] selCols, Column[] schema) {
this(selCols, schema, null);
}
public ColumnBasedRecordComparator(String[] selCols, Column[] schema, SortOrder[] sortOrder) {
super(schema);
this.sortOrder = sortOrder;
this.selIdxs = new int[selCols.length];
Map<String, Integer> reverseLookupMap = new HashMap<String, Integer>();
int i = 0;
for (Column c : schema) {
reverseLookupMap.put(c.getName(), i);
i++;
}
i = 0;
for (String col : selCols) {
selIdxs[i] = reverseLookupMap.get(col);
i++;
}
}
@Override
public int compare(Object[] l, Object[] r) {
int result = 0;
for (int i : selIdxs) {
if (r.length < i) {
return -1;
}
if (l.length < i) {
return 1;
}
if (sortOrder != null && sortOrder[i] == JobConf.SortOrder.DESC) {
result = compare(r[i], l[i], comparators[i]);
} else {
result = compare(l[i], r[i], comparators[i]);
}
if (result != 0) {
return result;
}
}
return 0;
}
}