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https://issues.apache.org/jira/browse/MAPREDUCE-7194?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated MAPREDUCE-7194:
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Labels: pull-request-available (was: )
> New Method For CombineFile
> --------------------------
>
> Key: MAPREDUCE-7194
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-7194
> Project: Hadoop Map/Reduce
> Issue Type: Improvement
> Components: mrv2
> Affects Versions: 3.2.0
> Reporter: David Mollitor
> Assignee: David Mollitor
> Priority: Major
> Labels: pull-request-available
>
> Rhe {{CombineFileInputFormat}} class is responsible for grouping blocks
> together to form larger splits. The current implementation is very naive.
> It iterates over the list of available blocks and as long as the current
> group of blocks is less than the maximum split size, it will keep added
> blocks. The check for if a split has reached its maximum size happens
> *after* each block is added. For example given a certain maximum "M", and
> two blocks which are both 7/8M, they will be grouped together to create a
> split which is 14/8M. If M is a large number, this split will be very large
> and not what the operator would expect.
> I'll propose a general clean up and also, enforcing that, unless a files
> cannot be split, that its splits will not be larger than the configured
> maximum size. This will provide operators a much more straight-forward way
> of calculating the expected number of splits.
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