StreamFeatureStatisticsQuery.java

/**
 * Copyright 2013-2015 Pierre Merienne
 *
 * 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.github.pmerienne.trident.ml.stats;

import java.util.ArrayList;
import java.util.List;

import com.github.pmerienne.trident.ml.util.KeysUtil;

import storm.trident.operation.TridentCollector;
import storm.trident.state.BaseQueryFunction;
import storm.trident.state.map.MapState;
import storm.trident.tuple.TridentTuple;
import backtype.storm.tuple.Values;

public class StreamFeatureStatisticsQuery extends BaseQueryFunction<MapState<StreamStatistics>, Double> {

	private static final long serialVersionUID = -8853291509350751320L;

	private String streamName;

	public StreamFeatureStatisticsQuery(String streamName) {
		this.streamName = streamName;
	}

	@Override
	public List<Double> batchRetrieve(MapState<StreamStatistics> state, List<TridentTuple> args) {
		List<Double> results = new ArrayList<Double>();

		List<StreamStatistics> statistics = state.multiGet(KeysUtil.toKeys(this.streamName));
		if (!statistics.isEmpty()) {
			// Get stream statistics
			StreamStatistics stat = statistics.get(0);

			for (TridentTuple request : args) {
				Integer featureIndex = this.getIndexFeatureIndex(request);
				QueryType queryType = this.getQueryType(request);
				Double result = this.getValue(stat, featureIndex, queryType);
				results.add(result);
			}

		}

		return results;
	}

	private Double getValue(StreamStatistics stat, Integer featureIndex, QueryType queryType) {
		Double value = null;
		StreamFeatureStatistics featureStatistics = stat.getFeaturesStatistics().get(featureIndex);

		switch (queryType) {
		case COUNT:
			value = featureStatistics.getCount().doubleValue();
			break;
		case MEAN:
			value = featureStatistics.getMean();
			break;
		case STDDEV:
			value = featureStatistics.getStdDev();
			break;
		case VARIANCE:
			value = featureStatistics.getVariance();
			break;
		}

		return value;
	}

	public void execute(TridentTuple tuple, Double result, TridentCollector collector) {
		collector.emit(new Values(result));
	}

	private Integer getIndexFeatureIndex(TridentTuple args) {
		return ((Number) args.get(0)).intValue();
	}

	private QueryType getQueryType(TridentTuple args) {
		return QueryType.valueOf(args.getString(1).toUpperCase());
	}

	private enum QueryType {
		COUNT, MEAN, VARIANCE, STDDEV;
	}
}