external/storm-sqe/src/main/java/com/jwplayer/sqe/trident/aggregator/HllCombinerAggregator.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.jwplayer.sqe.trident.aggregator;

import com.clearspring.analytics.stream.cardinality.CardinalityMergeException;
import com.clearspring.analytics.stream.cardinality.HyperLogLog;

import java.io.IOException;


public class HllCombinerAggregator extends CardinalityEstimatorCombinerAggregator {
    private int log2m;

    public HllCombinerAggregator(int log2m) {
        this.log2m = log2m;
    }

    @Override
    public byte[] combine(byte[] bitmap1, byte[] bitmap2) {
        try {
            HyperLogLog hll1 = HyperLogLog.Builder.build(bitmap1);
            HyperLogLog hll2 = HyperLogLog.Builder.build(bitmap2);
            hll1.addAll(hll2);
            return hll1.getBytes();
        } catch (CardinalityMergeException |IOException ex) {
            throw new RuntimeException(ex);
        }
    }

    @Override
    public byte[] zero() {
        try {
            return (new HyperLogLog(log2m)).getBytes();
        } catch(IOException ex) {
            throw new RuntimeException(ex);
        }
    }
}