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https://issues.apache.org/jira/browse/MRUNIT-88?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13427579#comment-13427579
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Dave Beech commented on MRUNIT-88:
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As I've been looking at grouping comparators and working on the "shuffle"
method in MRUNIT-127, I've had an idea about how we could test partitioners
under the current framework.
In the MapReduceDriver, as outputs come from the mapper we could apply a
user-specified partitioner and then organise the map outputs into numbered
buckets which represent the reduce slots. Then we would apply the sorting /
grouping logic currently found in "shuffle" to each bucket and call reduce
appropriately.
This would allow a more realistic test of mapreduce techniques like secondary
sort, which require the grouping & sorting comparators plus the partitioner to
all be correct and work properly together.
> MRUnit should support custom partitioners, comparator, and groupComparator
> --------------------------------------------------------------------------
>
> Key: MRUNIT-88
> URL: https://issues.apache.org/jira/browse/MRUNIT-88
> Project: MRUnit
> Issue Type: Improvement
> Reporter: Matthew Rathbone
> Labels: partitioners
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> We're building something that essentially does a secondary sort, to test that
> we need to be able to specify comparators and partitioners.
> Example:
> the following two tuple keys: (id1, source1), (id1, source2)
> should be grouped together based on the first value of the tuple, and their
> records should end up in the same reducer
> To do this we have our own custom partitioner / comparator, this is what we
> need to test through the whole pipeline in this way:
> MapReduceDriver.setPartitioner(p)
> MapReduceDriver.setGroupComparator(c)
> I'm not familiar enough with the MRUnit code to add this easily, but I
> suspect it would be pretty quick to do.
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