library/src/main/java/com/datatorrent/lib/streamquery/OrderByRule.java

/*
 * Copyright (c) 2013 DataTorrent, Inc. ALL Rights Reserved.
 *
 * Licensed 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.datatorrent.lib.streamquery;

import java.util.ArrayList;
import java.util.Map;
import java.util.TreeMap;

/**
 * Implements order by key name rule. <br>
 * <p>
 * <b>Properties : </b> <br>
 * <b> columnName : </b> Name of column for ordering tuples. <br>
 * @displayName OrderBy Rule
 * @category Streamquery
 * @tags orderby, sort, comparison
 * @since 0.3.3
 */
@SuppressWarnings("rawtypes")
public class OrderByRule<T extends Comparable>
{

  /**
   * column name for ordering tuples.
   */
  private String columnName;

  public OrderByRule(String name)
  {

    columnName = name;
  }

  /**
   * sort rows by each rule and emit result on output port.
   */
  @SuppressWarnings("unchecked")
  public ArrayList<Map<String, Object>> sort(ArrayList<Map<String, Object>> rows)
  {

    TreeMap<T, ArrayList<Map<String, Object>>> sorted = new TreeMap<T, ArrayList<Map<String, Object>>>();
    for (int i = 0; i < rows.size(); i++) {
      Map<String, Object> row = rows.get(i);
      if (row.containsKey(columnName)) {
        T value = (T) row.get(columnName);
        ArrayList<Map<String, Object>> list;
        if (sorted.containsKey(value)) {
          list = sorted.get(value);
        } else {
          list = new ArrayList<Map<String, Object>>();
          sorted.put(value, list);
        }
        list.add(row);
      }
    }
    ArrayList<Map<String, Object>> result = new ArrayList<Map<String, Object>>();
    for (Map.Entry<T, ArrayList<Map<String, Object>>> entry : sorted.entrySet()) {
      result.addAll(entry.getValue());
    }
    return result;
  }

  /**
   * @return the columnName
   */
  public String getColumnName()
  {

    return columnName;
  }

  /**
   * @param columnName
   *          the columnName to set
   */
  public void setColumnName(String columnName)
  {

    this.columnName = columnName;
  }
}