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From "rajeshbabu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-8874) PutCombiner is skipping KeyValues while combing puts of same row during bulkload
Date Fri, 05 Jul 2013 10:45:48 GMT
rajeshbabu created HBASE-8874:

             Summary: PutCombiner is skipping KeyValues while combing puts of same row during
                 Key: HBASE-8874
                 URL: https://issues.apache.org/jira/browse/HBASE-8874
             Project: HBase
          Issue Type: Bug
          Components: mapreduce
    Affects Versions: 0.95.1, 0.95.0
            Reporter: rajeshbabu
            Assignee: rajeshbabu
            Priority: Critical
             Fix For: 0.98.0, 0.95.2

While combining puts of same row in map phase we are using below logic in PutCombiner#reduce.
In for loop first time we will add one Put object to puts map. Next time onwards we are just
overriding key values of a family with key values of the same family in other put. So we are
mostly writing one Put object to map output and remaining will be skipped(data loss).
    Map<byte[], Put> puts = new TreeMap<byte[], Put>(Bytes.BYTES_COMPARATOR);
    for (Put p : vals) {
      if (!puts.containsKey(p.getRow())) {
        puts.put(p.getRow(), p);
      } else {

We need to change logic similar as below because we are sure the rowkey of all the puts will
be same.
    Put finalPut = null;
    Map<byte[], List<? extends Cell>> familyMap = null;
    for (Put p : vals) {
      if (finalPut==null) {
        finalPut = p;
        familyMap = finalPut.getFamilyMap();
      } else {
        for (Entry<byte[], List<? extends Cell>> entry : p.getFamilyMap().entrySet())
          List<? extends Cell> list = familyMap.get(entry.getKey());
          if (list == null) {
            familyMap.put(entry.getKey(), entry.getValue());
          } else {
    context.write(row, finalPut);

Also need to implement TODOs mentioned by Nick 
    // TODO: would be better if we knew <code>K row</code> and Put rowkey were
    // identical. Then this whole Put buffering business goes away.
    // TODO: Could use HeapSize to create an upper bound on the memory size of
    // the puts map 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.

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