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https://issues.apache.org/jira/browse/HADOOP-18842?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Steve Loughran updated HADOOP-18842:
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Component/s: fs/s3
> Support Overwrite Directory On Commit For S3A Committers
> --------------------------------------------------------
>
> Key: HADOOP-18842
> URL: https://issues.apache.org/jira/browse/HADOOP-18842
> Project: Hadoop Common
> Issue Type: New Feature
> Components: fs/s3
> Reporter: Syed Shameerur Rahman
> Priority: Major
> Labels: pull-request-available
>
> The goal is to add a new kind of commit mechanism in which the destination
> directory is cleared off before committing the file.
> *Use Case*
> In case of dynamicPartition insert overwrite queries, The destination
> directory which needs to be overwritten are not known before the execution
> and hence it becomes a challenge to clear off the destination directory.
>
> One approach to handle this is, The underlying engines/client will clear off
> all the destination directories before calling the commitJob operation but
> the issue with this approach is that, In case of failures while committing
> the files, We might end up with the whole of previous data being deleted
> making the recovery process difficult or time consuming.
>
> *Solution*
> Based on mode of commit operation either *INSERT* or *OVERWRITE* , During
> commitJob operations, The committer will map each destination directory with
> the commits which needs to be added in the directory and if the mode is
> *OVERWRITE* , The committer will delete the directory recursively and then
> commit each of the files in the directory. So in case of failures (worst
> case) The number of destination directory which will be deleted will be equal
> to the number of threads if we do it in multi-threaded way as compared to the
> whole data if it was done in the engine side.
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