You are viewing a plain text version of this content. The canonical link for it is here.
Posted to mapreduce-issues@hadoop.apache.org by "Todd Lipcon (JIRA)" <ji...@apache.org> on 2011/03/08 18:52:59 UTC
[jira] Resolved: (MAPREDUCE-2369) Using TableMapper Iterable
IntWritables not passed to the reducer in order put by mapper
[ 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.
>
>
--
This message is automatically generated by JIRA.
For more information on JIRA, see: http://www.atlassian.com/software/jira