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https://issues.apache.org/jira/browse/MRUNIT-129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13638898#comment-13638898
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Paulin Sanselme commented on MRUNIT-129:
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Did you have some time to review this patch ? Does it need some changes ?
> Key object re-use in Reducer is inconsistent with MapReduce behaviour (new
> API)
> -------------------------------------------------------------------------------
>
> Key: MRUNIT-129
> URL: https://issues.apache.org/jira/browse/MRUNIT-129
> Project: MRUnit
> Issue Type: Bug
> Affects Versions: 0.9.0
> Reporter: Dave Beech
> Fix For: 1.1.0
>
> Attachments: JIRA_129.patch, MRUNIT-129.unittest.patch
>
>
> Follow on issue from MRUNIT-127, also relating to grouping comparators.
> In the new MapReduce API Reducer's reduce method, you are passed a reference
> to a key and an Iterable for the values. What's not particularly clear is
> that as you iterate through the values, the value of the key is also changing
> silently. This is not usually noticeable, since the keys that were grouped
> often have the same value anyway, but with a custom grouping comparator this
> isn't necessarily the case.
> This is different to the old API, where you would get the first key in the
> group and this wouldn't change as you iterate over the values.
> MRUnit uses the "old API" style behaviour for both old and new APIs, so some
> unit tests may not give a consistent result to an actual mapreduce job.
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