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https://issues.apache.org/jira/browse/MRUNIT-129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13662975#comment-13662975
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Paulin Sanselme commented on MRUNIT-129:
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updateInput ans sortAndGroup are methods of ReduceFeeder.
ReduceFeeder provides methods for producing easily some reducer inputs in the
new format.
- updateInput is used internally to keep compatibility with the old way of
using mrunit. It is public to provide an easy way to update tests where we have
only one key and multiple values.
- sortAndGroup is used internally in MapReduceDriver to sort and group the map
outputs before giving them to the reducer. It is public to provide an easy way
of testing a Reducer alone with more complex inputs.
> 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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