library/src/main/java/com/datatorrent/lib/streamquery/OrderByOperator.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 com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.Operator;
import com.datatorrent.api.Operator.Unifier;

/**
 *  An implementation of Operator that provides sql order by operator semantic over live stream data. <br>
 * <p>
 * Input data rows are ordered by order rules, ordered result is emitted on output port. <br>
 * <br>
 *  *  <br>
 *  <b>StateFull : Yes,</b> Operator aggregates input over application window. <br>
 *  <b>Partitions : Yes, </b> This operator is also unifier on output port. <br>
 *  <br>
 * <b>Ports</b>:<br>
 * <b> inport : </b> Input hash map(row) port, expects HashMap&lt;String,Object&gt;<<br>
 * <b> outport : </b> Output hash map(row) port, emits  HashMap&lt;String,Object&gt;<br>
 * <br>
 * <b> Properties : </b> <br>
 * <b> oredrByRules : </b>List of order by rules for tuples.
 * @displayName: OrderBy
 * @category: streamquery
 * @tag: orderby operator
 * @since 0.3.5
 */
public class OrderByOperator implements Operator, Unifier<Map<String, Object>>
{
	/**
	 * Order by rules.
	 */
	ArrayList<OrderByRule<?>>	oredrByRules	= new ArrayList<OrderByRule<?>>();

	/**
	 * Descending flag.
	 */
	private boolean isDescending;
	
	/**
	 * collected rows.
	 */
	private ArrayList<Map<String, Object>> rows;

	/**
	 * Add order by rule.
	 */
	public void addOrderByRule(OrderByRule<?> rule)
	{
		oredrByRules.add(rule);
	}

	/**
   * @return isDescending
   */
  public boolean isDescending()
  {
	  return isDescending;
  }

	/**
   * @param set isDescending
   */
  public void setDescending(boolean isDescending)
  {
	  this.isDescending = isDescending;
  }

	@Override
  public void process(Map<String, Object> tuple)
  {
	  rows.add(tuple);
  }

  @Override
  public void beginWindow(long arg0)
  {
    rows = new ArrayList<Map<String, Object>>();
  }

  @Override
  public void endWindow()
  {
    for (int i=0; i < oredrByRules.size(); i++) {
      rows = oredrByRules.get(i).sort(rows);
    }
    if (isDescending) {
      for (int i=0; i < rows.size(); i++)  outport.emit(rows.get(i));
    } else {
      for (int i=rows.size()-1; i >= 0;  i--)  outport.emit(rows.get(i));
    }
  }

  @Override
  public void setup(OperatorContext arg0)
  {
    // TODO Auto-generated method stub
    
  }

  @Override
  public void teardown()
  {
    // TODO Auto-generated method stub
    
  }
  
  /**
   * Input port that takes a map of &lt;string,object&gt;.
   */
  public final transient DefaultInputPort<Map<String, Object>> inport = new DefaultInputPort<Map<String, Object>>() {
    @Override
    public void process(Map<String, Object> tuple)
    {
      rows.add(tuple);
    }
  };
  
  /**
   * Output port that emits a map of &lt;string,object&gt;.
   */
  public final transient DefaultOutputPort<Map<String, Object>> outport =  new DefaultOutputPort<Map<String, Object>>()
      {
         @Override
         public Unifier<Map<String, Object>> getUnifier() {
           OrderByOperator unifier = new OrderByOperator();
           for (int i=0; i < oredrByRules.size(); i++) {
             unifier.addOrderByRule(oredrByRules.get(i));
           }
           unifier.setDescending(isDescending);
           return unifier;
         }
      };
}