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https://issues.apache.org/jira/browse/CRUNCH-132?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13575611#comment-13575611
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Josh Wills commented on CRUNCH-132:
-----------------------------------
Definitely +1 for WriteMode.
Regarding making the naiive:
pipeline.write(pcollect1, target);
pipeline.write(pcollect2, target);
pipeline.run();
throw an exception, I think that the easiest way to do that would be to have
MRPipeline check to see if an equal Target is written to more than once w/o a
WriteMode.APPEND being specified. I think I can make it work, I'll cook up
something this evening and post it tomorrow.
> Add configurable behavior for when a pipeline output directory already exists
> -----------------------------------------------------------------------------
>
> Key: CRUNCH-132
> URL: https://issues.apache.org/jira/browse/CRUNCH-132
> Project: Crunch
> Issue Type: Improvement
> Affects Versions: 0.4.0
> Reporter: Dave Beech
> Assignee: Josh Wills
> Attachments: CRUNCH-132.patch, CRUNCH-132-proto.patch
>
>
> Usually when you run a mapreduce job and the output directory already exists,
> the job fails (won't start). A Crunch job does run, but results in the output
> data being duplicated in the output directory with numbered files that follow
> on from the previous run.
> Example
> Run 1, single reducer /output -> /output/part-r-00000
> Run 2, single reducer /output -> /output/part-r-00000, /output/part-r-00001
> I didn't realise I'd run my job twice, so when I looked in the directory it
> seemed that there had been 2 reducers and somehow the output had been
> generated twice, which was confusing.
> I realise this may be by design, but it feels wrong to me. I'd prefer if the
> behaviour of a standard mapreduce job was preserved.
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