/**
    *
    * 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 org.apache.hadoop.hbase.mapreduce;
  
  import java.io.IOException;
  import java.util.List;
  import java.util.Map.Entry;
  import java.util.Map;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.hbase.classification.InterfaceAudience;
  import org.apache.hadoop.hbase.classification.InterfaceStability;
  import org.apache.hadoop.hbase.Cell;
  import org.apache.hadoop.hbase.KeyValue;
  import org.apache.hadoop.hbase.KeyValueUtil;
  import org.apache.hadoop.hbase.client.Put;
  import org.apache.hadoop.mapreduce.Reducer;
  
  /**
   * Combine Puts. Merges Put instances grouped by <code>K</code> into a single
   * instance.
   * @see TableMapReduceUtil
   */
  @InterfaceAudience.Public
  @InterfaceStability.Evolving
  public class PutCombiner<K> extends Reducer<K, Put, K, Put> {
    private static final Log LOG = LogFactory.getLog(PutCombiner.class);
  
    @Override
    protected void reduce(K row, Iterable<Put> vals, Context context)
        throws IOException, InterruptedException {
      // Using HeapSize to create an upper bound on the memory size of
      // the puts and flush some portion of the content while looping. This
      // flush could result in multiple Puts for a single rowkey. That is
      // acceptable because Combiner is run as an optimization and it's not
      // critical that all Puts are grouped perfectly.
      long threshold = context.getConfiguration().getLong(
          "putcombiner.row.threshold", 1L * (1<<30));
      int cnt = 0;
      long curSize = 0;
      Put put = null;
      Map<byte[], List<Cell>> familyMap = null;
      for (Put p : vals) {
        cnt++;
        if (put == null) {
          put = p;
          familyMap = put.getFamilyCellMap();
        } else {
          for (Entry<byte[], List<Cell>> entry : p.getFamilyCellMap()
              .entrySet()) {
            List<Cell> cells = familyMap.get(entry.getKey());
            List<Cell> kvs = (cells != null) ? (List<Cell>) cells : null;
            for (Cell cell : entry.getValue()) {
              KeyValue kv = KeyValueUtil.ensureKeyValue(cell);
              curSize += kv.heapSize();
              if (kvs != null) {
                kvs.add(kv);
              }
            }
            if (cells == null) {
              familyMap.put(entry.getKey(), entry.getValue());
            }
          }
          if (cnt % 10 == 0) context.setStatus("Combine " + cnt);
          if (curSize > threshold) {
            if (LOG.isDebugEnabled()) {
              LOG.debug(String.format("Combined %d Put(s) into %d.", cnt, 1));
            }
            context.write(row, put);
            put = null;
            curSize = 0;
            cnt = 0;
          }
        }
      }
      if (put != null) {
        if (LOG.isDebugEnabled()) {
          LOG.debug(String.format("Combined %d Put(s) into %d.", cnt, 1));
        }
        context.write(row, put);
      }
    }
 }