content: /*
   * 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.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[] sortOrders;
  
    /**
     * 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.sortOrders = 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[] sortOrders) {
      super(schema);
  
      if (sortOrders != null && selCols.length != sortOrders.length) {
        throw new IllegalArgumentException(
            "Number of sort column is not equal to length of sort order array.");
      }
  
      this.sortOrders = sortOrders;
      this.selIdxs = new int[selCols.length];
      Map<String, Integer> reverseLookupMap = new HashMap<>();
      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;
      int index = 0;
      for (int i : selIdxs) {
        if (r.length < i) {
          if (sortOrders != null && sortOrders[index] == SortOrder.DESC) {
            return 1;
          }
          return -1;
        }
        if (l.length < i) {
          if (sortOrders != null && sortOrders[index] == SortOrder.DESC) {
            return -1;
          }
          return 1;
        }
        result = compare(l[i], r[i], comparators[i]);
        if (result != 0) {
          if (sortOrders != null && sortOrders.length == selIdxs.length
              && sortOrders[index] == SortOrder.DESC) {
            return (0 - result);
          }
          return result;
        }
        index++;
      }
      return 0;
    }
  }
  