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https://issues.apache.org/jira/browse/CRUNCH-218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13682143#comment-13682143
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Gabriel Reid commented on CRUNCH-218:
-------------------------------------
Ok, so the actual use case is the union of what I was talking about and what
Josh's patch does :-)
Like I said before, I definitely like the idea of both of these things, but I
do think that we need to have a way of saying that we want to overwrite
something that has been written in checkpoint mode previously. I'm thinking
that this could either be done automatically, by checking the creation time of
the data that is used to create the checkpointed data, or by having some kind
of run mode to force overwriting checkpointed data. Or maybe we shouldn't worry
about that, and just advise extra caution for stale data when writing in
checkpoint mode.
> Add new Target.WriteMode to skip the write and continue pipeline if an output
> target exists
> -------------------------------------------------------------------------------------------
>
> Key: CRUNCH-218
> URL: https://issues.apache.org/jira/browse/CRUNCH-218
> Project: Crunch
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.6.0
> Reporter: Dave Beech
> Assignee: Josh Wills
> Priority: Minor
> Attachments: CRUNCH-218b.patch, CRUNCH-218.patch
>
>
> Quite often I write pipelines which persist data to the filesystem midway
> through the process, and then carry on doing further work.
> If this intermediate data is already present, I think it would be good if I
> could set a write mode which skips over this first half of processing. This
> way I'd avoid running jobs unnecessarily and wasting cluster resources
> regenerating data I already have.
> Example:
> PCollection<B> inter =
> pipeline.read(source).parallelDo(something).parallelDo(somethingElse);
> inter.write(At.sequenceFile('output'), WriteMode.SKIP_IF_EXISTS);
> PCollection<C> final = inter.parallelDo(moreWork);
>
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