com.datatorrent.lib.algo.InvertIndex 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.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Operator.Unifier;
import com.datatorrent.api.annotation.OperatorAnnotation;

import com.datatorrent.lib.util.BaseKeyValueOperator;

/**
 * This operator takes a stream of key value pairs each window,
 * and outputs a set of inverted key value pairs at the end of each window.
 * 
 * Inverts the index and sends out the tuple on output port "index" at the end of the window.
 * 
 * 
 * This is an end of window operator

 * 

 * StateFull : Yes,  tuple are compare across application window(s). 

 * Partitions : Yes,  inverted indexes are unified by instance of same operator. 

 * 

 * 

 * Ports:

 * data: expects <K,V>

 * index: emits <V,ArrayList<K>>(1); one HashMap per V

 * 

 * 
 *
 * @displayName Invert Key Value Pairs
 * @category Stream Manipulators
 * @tags key value
 *
 * @since 0.3.2
 */

@OperatorAnnotation(partitionable = true)
public class InvertIndex extends BaseKeyValueOperator implements Unifier>>
{
  /**
   * Inverted key/value map.
   */
  protected HashMap> map = new HashMap>();

  /**
   * The input port on which key value pairs are received.
   */
  public final transient DefaultInputPort> data = new DefaultInputPort>()
  {
    /**
     * Reverse indexes a HashMap> tuple
     */
    @Override
    public void process(HashMap tuple)
    {
      for (Map.Entry e: tuple.entrySet()) {
        if (e.getValue() == null) { // error tuple?
          continue;
        }
        insert(e.getValue(), cloneKey(e.getKey()));
      }
    }
  };

  /**
   * The output port on which inverted key value pairs are emitted.
   */
  public final transient DefaultOutputPort>> index = new DefaultOutputPort>>()
  {
    @Override
    public Unifier>> getUnifier()
    {
      return new InvertIndex();
    }
  };

  /**
   *
   * Returns the ArrayList stored for a key
   *
   * @param key
   */
  void insert(V val, K key)
  {
    ArrayList list = map.get(val);
    if (list == null) {
      list = new ArrayList(4);
      map.put(cloneValue(val), list);
    }
    list.add(key);
  }

  /**
   * Emit all the data and clear the hash
   * Clears internal data
   */
  @Override
  public void endWindow()
  {
    for (Map.Entry> e: map.entrySet()) {
      HashMap> tuple = new HashMap>(1);
      tuple.put(e.getKey(), e.getValue());
      index.emit(tuple);
    }
    map.clear();
  }

  /**
   * Unifier override.
   */
  @Override
  public void process(HashMap> tuple)
  {
    for (Map.Entry> e: tuple.entrySet()) {
      ArrayList keys;
      if (map.containsKey(e.getKey())) {
        keys = map.remove(e.getKey());
      } else {
        keys = new ArrayList();
      }
      keys.addAll(e.getValue());
    }
  }
}