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From "rajeshbabu (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-8874) PutCombiner is skipping KeyValues while combining puts of same row during bulkload
Date Mon, 15 Jul 2013 13:20:48 GMT

     [ https://issues.apache.org/jira/browse/HBASE-8874?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

rajeshbabu updated HBASE-8874:
------------------------------

    Attachment: HBASE-8874_trunk.patch

Patch for trunk. Verified the patch in the cluster 
1) by taking same rowkey in multiple lines then also its giving all keyvalues.
2)configured putcombiner.row.threshold to small value and checked mapoutput file which has
multiple writes to same row.
Its working fine.

Please review it.

                
> PutCombiner is skipping KeyValues while combining puts of same row during bulkload
> ----------------------------------------------------------------------------------
>
>                 Key: HBASE-8874
>                 URL: https://issues.apache.org/jira/browse/HBASE-8874
>             Project: HBase
>          Issue Type: Bug
>          Components: mapreduce
>    Affects Versions: 0.95.0, 0.95.1
>            Reporter: rajeshbabu
>            Assignee: rajeshbabu
>            Priority: Critical
>             Fix For: 0.98.0, 0.95.2
>
>         Attachments: HBASE-8874_trunk.patch
>
>
> 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).
> {code}
>     Map<byte[], Put> puts = new TreeMap<byte[], Put>(Bytes.BYTES_COMPARATOR);
>     for (Put p : vals) {
>       cnt++;
>       if (!puts.containsKey(p.getRow())) {
>         puts.put(p.getRow(), p);
>       } else {
>         puts.get(p.getRow()).getFamilyMap().putAll(p.getFamilyMap());
>       }
>     }
> {code}
> We need to change logic similar as below because we are sure the rowkey of all the puts
will be same.
> {code}
>     Put finalPut = null;
>     Map<byte[], List<? extends Cell>> familyMap = null;
>     for (Put p : vals) {
>      cnt++;
>       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 {
>             (((List<KeyValue>)list)).addAll((List<KeyValue>)entry.getValue());
>           }
>         }
>       }
>     }
>     context.write(row, finalPut);
> {code}
> Also need to implement TODOs mentioned by Nick 
> {code}
>     // 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.
> {code}

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