library/src/main/java/org/apache/apex/malhar/lib/util/UnifierKeyValRange.java

/**
 * 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 org.apache.apex.malhar.lib.util;

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

import com.datatorrent.api.Context.OperatorContext;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.Operator.Unifier;

/**
 * This unifier consumes key value pairs, where the key is an object and the value is a number. 
 * The unifier emits the minimum and maximum value for each key in a map at the end of each application window.
 * <p>
 * This unifier uses round robin partitioning.
 * </p>
 * @displayName Unifier Key Value Range
 * @category Algorithmic
 * @tags numeric, key value
 * @since 0.3.2
 */
public class UnifierKeyValRange<K, V extends Number> implements Unifier<KeyValPair<K, HighLow<V>>>
{
  /**
   * This is the output port that emits key value pairs which map keys to a minimum and maximum.
   */
  public final transient DefaultOutputPort<KeyValPair<K, HighLow<V>>> mergedport = new DefaultOutputPort<KeyValPair<K, HighLow<V>>>();

  /**
   * combines the tuple into a single final tuple which is emitted in endWindow
   * @param tuple incoming tuple from a partition
   */
  @Override
  public void process(KeyValPair<K, HighLow<V>> tuple)
  {
    HighLow<V> val = map.get(tuple.getKey());
    if (val == null) {
      val = new HighLow(tuple.getValue().getHigh(), tuple.getValue().getLow());
    }

    if (val.getHigh().doubleValue() < tuple.getValue().getHigh().doubleValue()) {
      val.setHigh(tuple.getValue().getHigh());
    }
    if (val.getLow().doubleValue() > tuple.getValue().getLow().doubleValue()) {
      val.setLow(tuple.getValue().getLow());
    }
  }

  HashMap<K, HighLow<V>> map = new HashMap<K, HighLow<V>>();

  /**
   * a no op
   * @param windowId
   */
  @Override
  public void beginWindow(long windowId)
  {
  }


  /**
   * emits mergedTuple on mergedport if it is not empty
   */
  @SuppressWarnings({ "unchecked", "rawtypes" })
  @Override
  public void endWindow()
  {
    if (!map.isEmpty()) {
      for (Map.Entry<K, HighLow<V>> e: map.entrySet()) {
        mergedport.emit(new KeyValPair(e.getKey(), new HighLow(e.getValue().getHigh(), e.getValue().getLow())));
      }
      map.clear();
    }
  }

  /**
   * a no-op
   * @param context
   */
  @Override
  public void setup(OperatorContext context)
  {
  }

  /**
   * a noop
   */
  @Override
  public void teardown()
  {
  }
}