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

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

import org.apache.commons.lang.mutable.MutableInt;

import com.datatorrent.api.DefaultInputPort;
import com.datatorrent.api.DefaultOutputPort;
import com.datatorrent.api.StreamCodec;
import com.datatorrent.api.annotation.InputPortFieldAnnotation;
import com.datatorrent.api.annotation.OutputPortFieldAnnotation;
import com.datatorrent.lib.util.BaseKeyValueOperator;
import com.datatorrent.lib.util.KeyValPair;
import com.datatorrent.lib.util.UnifierCountOccurKey;

/**
 * This Operator aggregates occurrence of keys in <key,value> pair at input port.<Key,Occurrence count> pair is emitted for each input on output port.
 * <p>
 * <br>
 * StateFull : Yes, key occurrence is aggregated over windows. <br>
 * Partitions : Yes, count occurrence unifier at output port. <br>
 * <br>
 * <b>Ports</b>:<br>
 * <b>data</b>: expects KeyValPair&lt;K,V&gt;<br>
 * <b>count</b>: emits KeyValPair&lt;K,Integer&gt;</b><br>
 * <br>
 * @displayName Count Key Value
 * @category Math
 * @tags count, key value, aggregate
 * @since 0.3.3
 */
public class CountKeyVal<K, V> extends BaseKeyValueOperator<K, V>
{

	/**
	 * Key occurrence count map.
	 */
	protected HashMap<K, MutableInt> counts = new HashMap<K, MutableInt>();

	/**
	 * Input data port that takes key value pair.
	 */
	public final transient DefaultInputPort<KeyValPair<K, V>> data = new DefaultInputPort<KeyValPair<K, V>>()
	{
		/**
		 * For each tuple (a key value pair): Adds the values for each key, Counts
		 * the number of occurrence of each key
		 */
		@Override
		public void process(KeyValPair<K, V> tuple)
		{
			K key = tuple.getKey();
			MutableInt count = counts.get(key);
			if (count == null) {
				count = new MutableInt(0);
				counts.put(cloneKey(key), count);
			}
			count.increment();
		}

		@Override
		public StreamCodec<KeyValPair<K, V>> getStreamCodec()
		{
			return getKeyValPairStreamCodec();
		}
	};

	/**
	 * Key, occurrence value pair output port.
	 */
	@OutputPortFieldAnnotation(optional = true)
	public final transient DefaultOutputPort<KeyValPair<K, Integer>> count = new DefaultOutputPort<KeyValPair<K, Integer>>()
	{
		@Override
		public UnifierCountOccurKey<K> getUnifier()
		{
			return new UnifierCountOccurKey<K>();
		}
	};

	/**
	 * Emits on all ports that are connected. Data is computed during process on
	 * input port and endWindow just emits it for each key. Clears the internal
	 * data if resetAtEndWindow is true.
	 */
	@SuppressWarnings({ "unchecked", "rawtypes" })
	@Override
	public void endWindow()
	{
		for (Map.Entry<K, MutableInt> e : counts.entrySet()) {
			count.emit(new KeyValPair(e.getKey(),
					new Integer(e.getValue().intValue())));
		}
		counts.clear();
	}
}