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