com.datatorrent.lib.algo.TopN Maven / Gradle / Ivy

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/**
 * 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.datatorrent.lib.algo;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Operator.Unifier;
import com.datatorrent.api.annotation.OperatorAnnotation;

import com.datatorrent.lib.util.AbstractBaseNNonUniqueOperatorMap;

/**
 * This operator orders tuples per key and emits the top N tuples per key at the end of the window.
 * 
 * Orders tuples per key and emits top N tuples per key on end of window.
 * 
 * 
 * This is an end of window module.

 * 

 * StateFull : Yes,  Tuple are aggregated across application window(s). 

 * Partitions : Yes,  Top values are unified on output port. 

 * Ports:

 * data: Input data port expects HashMap<K,V>

 * top: Output data port, emits HashMap<K, ArrayList<V>>

 * 

 * Properties:

 * N: The number of top values to be emitted per key

 * 

 * Specific compile time checks are:

 * N: Has to be >= 1

 * 

 * 
 *
 * @displayName Top N Values Per Key
 * @category Stats and Aggregations
 * @tags filter, rank
 *
 * @since 0.3.3
 */

@OperatorAnnotation(partitionable = true)
public class TopN extends AbstractBaseNNonUniqueOperatorMap implements Unifier>>
{
  /**
   * The output port which emits the top N values per key.
   */
  public final transient DefaultOutputPort>> top = new DefaultOutputPort>>()
  {
    @Override
    public Unifier>> getUnifier()
    {
      TopN unifier = new TopN();
      unifier.setN(getN());
      return unifier;
    }
  };

  /**
   * returns true
   * @return true
   */
  @Override
  public boolean isAscending()
  {
    return true;
  }

  /**
   * Emits tuple on port "top"
   */
  @Override
  public void emit(HashMap> tuple)
  {
    top.emit(tuple);
  }

  @Override
  public void process(HashMap> tuple)
  {
    for (Map.Entry> entry : tuple.entrySet()) {
      for (V value : entry.getValue()) {
        HashMap item = new HashMap();
        item.put(entry.getKey(), value);
        this.processTuple(item);
      }
    }
  }

  /**
   * Top N tuples per key
   * @param val
   */
  @Override
  public void setN(int val)
  {
    super.setN(val);
  }
}