job/src/main/java/com/kylinolap/job/hadoop/cardinality/ColumnCardinalityMapper.java

/*
 * Copyright 2013-2014 eBay Software Foundation
 *
 * 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.kylinolap.job.hadoop.cardinality;

import com.kylinolap.common.hll.HyperLogLogPlusCounter;
import com.kylinolap.cube.kv.RowConstants;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.io.BytesWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;

import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.StringTokenizer;

/**
 * @author Jack
 */
public class ColumnCardinalityMapper<T> extends Mapper<T, Text, IntWritable, BytesWritable> {

    private Map<Integer, HyperLogLogPlusCounter> hllcMap = new HashMap<Integer, HyperLogLogPlusCounter>();
    public static final String DEFAULT_DELIM = ",";

    @Override
    public void map(T key, Text value, Context context) throws IOException, InterruptedException {
        String delim = context.getConfiguration().get(HiveColumnCardinalityJob.KEY_INPUT_DELIM);
        if (delim == null) {
            delim = DEFAULT_DELIM;
        }
        String line = value.toString();
        StringTokenizer tokenizer = new StringTokenizer(line, delim);
        int i = 1;
        while (tokenizer.hasMoreTokens()) {
            String temp = tokenizer.nextToken();
            getHllc(i).add(Bytes.toBytes(temp));
            i++;
        }
    }

    private HyperLogLogPlusCounter getHllc(Integer key) {
        if (!hllcMap.containsKey(key)) {
            hllcMap.put(key, new HyperLogLogPlusCounter());
        }
        return hllcMap.get(key);
    }

    @Override
    protected void cleanup(Context context) throws IOException, InterruptedException {
        Iterator<Integer> it = hllcMap.keySet().iterator();
        while (it.hasNext()) {
            int key = it.next();
            HyperLogLogPlusCounter hllc = hllcMap.get(key);
            ByteBuffer buf = ByteBuffer.allocate(RowConstants.ROWVALUE_BUFFER_SIZE);
            buf.clear();
            hllc.writeRegisters(buf);
            buf.flip();
            context.write(new IntWritable(key), new BytesWritable(buf.array()));
        }
    }

}