/**
    *
    * 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.util.Iterator;
  import java.util.List;
  import java.util.TreeSet;
  
  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.hbase.io.ImmutableBytesWritable;
  import org.apache.hadoop.mapreduce.Reducer;
  import org.apache.hadoop.util.StringUtils;
  
  /**
   * Emits sorted Puts.
   * Reads in all Puts from passed Iterator, sorts them, then emits
   * Puts in sorted order.  If lots of columns per row, it will use lots of
   * memory sorting.
   * @see HFileOutputFormat
   * @see KeyValueSortReducer
   */
  @InterfaceAudience.Public
  @InterfaceStability.Stable
  public class PutSortReducer extends
      Reducer<ImmutableBytesWritable, Put, ImmutableBytesWritable, KeyValue> {
    
    @Override
    protected void reduce(
        ImmutableBytesWritable row,
        java.lang.Iterable<Put> puts,
        Reducer<ImmutableBytesWritable, Put,
                ImmutableBytesWritable, KeyValue>.Context context)
        throws java.io.IOException, InterruptedException
    {
      // although reduce() is called per-row, handle pathological case
      long threshold = context.getConfiguration().getLong(
          "putsortreducer.row.threshold", 1L * (1<<30));
      Iterator<Put> iter = puts.iterator();
      while (iter.hasNext()) {
        TreeSet<KeyValue> map = new TreeSet<KeyValue>(KeyValue.COMPARATOR);
        long curSize = 0;
        // stop at the end or the RAM threshold
        while (iter.hasNext() && curSize < threshold) {
          Put p = iter.next();
          for (List<Cell> cells: p.getFamilyCellMap().values()) {
            for (Cell cell: cells) {
              KeyValue kv = KeyValueUtil.ensureKeyValue(cell);
              map.add(kv);
              curSize += kv.heapSize();
            }
          }
        }
        context.setStatus("Read " + map.size() + " entries of " + map.getClass()
            + "(" + StringUtils.humanReadableInt(curSize) + ")");
        int index = 0;
        for (KeyValue kv : map) {
          context.write(row, kv);
          if (++index % 100 == 0)
            context.setStatus("Wrote " + index);
        }
  
        // if we have more entries to process
        if (iter.hasNext()) {
          // force flush because we cannot guarantee intra-row sorted order
          context.write(null, null);
        }
      }
    }
  }