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Posted to mapreduce-dev@hadoop.apache.org by "Cummins, Robert [USA]" <cu...@bah.com> on 2011/02/22 16:45:53 UTC
mapreduce passed parameter value ordering
Is the following acceptable or is an enhancement/bug fix needed?
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.
Suggestion: It would be a helpful and simple feature to have chronological
order guaranteed as a facility for identification by the reducer.