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https://issues.apache.org/jira/browse/HIVE-15093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15629478#comment-15629478
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Illya Yalovyy commented on HIVE-15093:
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-1
This approach will block any possible optimization in a connector library. File
system level operation should not be re-implemented in application. Thread pool
is not the only option here, different blob stores have different ways to
optimize move use case. An application should be blobstore agnostic. Does it
make sense?
> S3-to-S3 Renames: Files should be moved individually rather than at a
> directory level
> -------------------------------------------------------------------------------------
>
> Key: HIVE-15093
> URL: https://issues.apache.org/jira/browse/HIVE-15093
> Project: Hive
> Issue Type: Sub-task
> Components: Hive
> Affects Versions: 2.1.0
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Attachments: HIVE-15093.1.patch, HIVE-15093.2.patch,
> HIVE-15093.3.patch, HIVE-15093.4.patch, HIVE-15093.5.patch,
> HIVE-15093.6.patch, HIVE-15093.7.patch
>
>
> Hive's MoveTask uses the Hive.moveFile method to move data within a
> distributed filesystem as well as blobstore filesystems.
> If the move is done within the same filesystem:
> 1: If the source path is a subdirectory of the destination path, files will
> be moved one by one using a threapool of workers
> 2: If the source path is not a subdirectory of the destination path, a single
> rename operation is used to move the entire directory
> The second option may not work well on blobstores such as S3. Renames are not
> metadata operations and require copying all the data. Client connectors to
> blobstores may not efficiently rename directories. Worst case, the connector
> will copy each file one by one, sequentially rather than using a threadpool
> of workers to copy the data (e.g. HADOOP-13600).
> Hive already has code to rename files using a threadpool of workers, but this
> only occurs in case number 1.
> This JIRA aims to modify the code so that case 1 is triggered when copying
> within a blobstore. The focus is on copies within a blobstore because
> needToCopy will return true if the src and target filesystems are different,
> in which case a different code path is triggered.
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