library/src/main/java/com/datatorrent/lib/math/MaxKeyVal.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 com.datatorrent.lib.math;

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

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.StreamCodec;
import com.datatorrent.lib.util.BaseNumberKeyValueOperator;
import com.datatorrent.lib.util.KeyValPair;

/**
 *
 * This operator emits maximum of all values sub-classed from Number at end of window for each key in KeyValPair.
 * <p>
 * <br>
 * <b>Ports</b>:<br>
 * <b>data</b>: expects KeyValPair&lt;K,V extends Number&gt;<br>
 * <b>max</b>: emits KeyValPair&lt;K,V extends Number&gt;, one entry per key<br>
 * <br>
 * <b>Properties</b>:<br>
 * <b>inverse</b>: if set to true the key in the filter will block tuple<br>
 * <b>filterBy</b>: List of keys to filter on<br>
 * <br>
 * @displayName Maximum Key Value
 * @category Math
 * @tags maximum, numeric, key value
 * @since 0.3.2
 */
public class MaxKeyVal<K, V extends Number> extends BaseNumberKeyValueOperator<K, V>
{
  /**
   * Input port that takes a key value pair and compares to max and stores the new max.
   */
  public final transient DefaultInputPort<KeyValPair<K, V>> data = new DefaultInputPort<KeyValPair<K, V>>()
  {
    /**
     * For each key, updates the hash if the new value is a new max.
     */
    @Override
    public void process(KeyValPair<K, V> tuple)
    {
      K key = tuple.getKey();
      V tval = tuple.getValue();
      if (!doprocessKey(key) || (tval == null)) {
        return;
      }
      V val = highs.get(key);
      if (val == null) {
        val = tval;
        highs.put(cloneKey(key), val);
      } else if (val.doubleValue() < tval.doubleValue()) {
        highs.put(key, tval);
      }
    }

    /**
     * Set StreamCodec used for partitioning.
     */
    @Override
    public StreamCodec<KeyValPair<K, V>> getStreamCodec()
    {
      return getKeyValPairStreamCodec();
    }
  };

  /**
   * Max value output port.
   */
  public final transient DefaultOutputPort<KeyValPair<K, V>> max = new DefaultOutputPort<KeyValPair<K, V>>();

  protected HashMap<K, V> highs = new HashMap<K, V>();

  /**
   * Emits all key,max value pairs.
   * Override getValue() if you have your own class extended from Number.
   * Clears internal data. Node only works in windowed mode.
   */
  @SuppressWarnings({ "rawtypes", "unchecked" })
  @Override
  public void endWindow()
  {
    if (!highs.isEmpty()) {
      for (Map.Entry<K, V> e: highs.entrySet()) {
        max.emit(new KeyValPair(e.getKey(), e.getValue()));
      }
      clearCache();
    }
  }

  public void clearCache()
  {
    highs.clear();
  }
}