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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HBASE-7743) KeyValueSortReducer and PutSortReducers buffer entire value-groups in memory
Date Sat, 02 Feb 2013 01:11:11 GMT
Nick Dimiduk created HBASE-7743:
-----------------------------------

             Summary: KeyValueSortReducer and PutSortReducers buffer entire value-groups in
memory
                 Key: HBASE-7743
                 URL: https://issues.apache.org/jira/browse/HBASE-7743
             Project: HBase
          Issue Type: Improvement
          Components: mapreduce
            Reporter: Nick Dimiduk


The mapreduce package provides two Reducer implementations, KeyValueSortReducer and PutSortReducer,
which are used by Import, ImportTsv, and WALPlayer in conjunction with the HFileOutputFormat.
Both of these implementations make use of a TreeSet to sort values matching a key. This reducer
will OOM when rows are large.

A better solution would be to implement secondary sort of the values. That way hadoop sorts
the records, spilling to disk when necessary.

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