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Date: Wed, 16 Mar 2011 23:30:29 +0000 (UTC)
From: "Bob Cummins (JIRA)" <jira@apache.org>
To: issues@hbase.apache.org
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Subject: [jira] Commented: (HBASE-3646) When mapper writes multiple values
 for a key keep chronological order of values
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    [ https://issues.apache.org/jira/browse/HBASE-3646?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13007739#comment-13007739 ] 

Bob Cummins commented on HBASE-3646:
------------------------------------

Yes, and an index argument for the write method could be helpful.


> When mapper writes multiple values for a key keep chronological order of values
> -------------------------------------------------------------------------------
>
>                 Key: HBASE-3646
>                 URL: https://issues.apache.org/jira/browse/HBASE-3646
>             Project: HBase
>          Issue Type: New Feature
>          Components: client
>    Affects Versions: 0.90.1
>         Environment: Cloudera 3.5 VM 
> TableMapper<ImmutableBytesWritable,IntWritable>
> TableReducer<ImmutableBytesWritable,IntWritable, ImmutableBytesWritable>
>            Reporter: Bob Cummins
>            Priority: Minor
>
> When mapper writes multiple values for a key, the underlying collection class maps each of the values to the key, but not always in chronological order. If chronological order were guaranteed each of the values mapped to the key, each of the values could be understood as specific and different parameters between the mapper and the reducer.
> I've done little tricks like having the mapper flag one a the values by making it a negative number, which the reducer recognizes and can write it to hbase as a unique column value.This is a kluge workaround which it would be nice to not have to do.
> Used to formulate this suggestion:
> TableMapper<ImmutableBytesWritable,IntWritable>
> TableReducer<ImmutableBytesWritable,IntWritable, ImmutableBytesWritable>

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