[jira] [Commented] (HBASE-7743) Replace *SortReducers with Hadoop Secondary Sort

["Nick Dimiduk (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-7743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13592753#comment-13592753 ] 

Nick Dimiduk commented on HBASE-7743:
-------------------------------------

bq. I could see it going away if we emitted Key and comparator was KeyValues's Key comparator.

This quote is from [~stack] on HBASE-7747. Can you follow-up on this comment. Is KeyValue$KeyComparator the correct comparator to use for a Hadoop secondary sort before generating an HFile or Mutation instances per row? KeyValueSortReducer uses KeyValue.COMPARATOR which is an instance of KeyValue$KVComparator.
                
> Replace *SortReducers with Hadoop Secondary Sort
> ------------------------------------------------
>
>                 Key: HBASE-7743
>                 URL: https://issues.apache.org/jira/browse/HBASE-7743
>             Project: HBase
>          Issue Type: Improvement
>          Components: mapreduce, Performance
>            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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