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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Resolved: (MAPREDUCE-2369) Using TableMapper Iterable IntWritables not passed to the reducer in order put by mapper
Date Tue, 08 Mar 2011 17:52:59 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-2369?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Todd Lipcon resolved MAPREDUCE-2369.
------------------------------------

    Resolution: Invalid

This is as designed - MR provides no guarantee that the order of values in the reducer is
the same as the order written by mappers.

> Using TableMapper Iterable IntWritables not passed to the reducer in order put by mapper
> ----------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-2369
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-2369
>             Project: Hadoop Map/Reduce
>          Issue Type: Improvement
>          Components: client
>    Affects Versions: 0.20.2
>         Environment: Cloudera VM 3.5
>            Reporter: Bob Cummins
>            Priority: Minor
>
> For mapper class:
>       class Mapper1 extends TableMapper<ImmutableBytesWritable,IntWritable>
> With reducer class:
>      class Reducer1 extends TableReducer<ImmutableBytesWritable,IntWritable, ImmutableBytesWritable>
> Iterable<IntWritable> values are usually received by the reducer in the
> order the values are written to the context by the mapper. However in my
> testing about 5% of cases, the same order is not maintained, and the ability
> of the reducer to categorize a value by order lost.
> Chronological order guaranteed would serve as a facility for identification by the reducer.
>  
>  

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