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https://issues.apache.org/jira/browse/HIVE-15546?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sahil Takiar updated HIVE-15546:
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Attachment: HIVE-15546.2.patch
Original attempt was to just remove the check for empty input paths, but that
turned out to be much more difficult than I originally thought.
Attaching a revised path that makes it multi-threaded. I decided to re-use the
config mapred.dfsclient.parallelism.max since it seems to be used for other
methods in the Utilities class relevant to MR job setup (e.g. content summary
calculations).
> Optimize Utilities.getInputPaths()
> ----------------------------------
>
> Key: HIVE-15546
> URL: https://issues.apache.org/jira/browse/HIVE-15546
> Project: Hive
> Issue Type: Sub-task
> Components: Hive
> Reporter: Sahil Takiar
> Assignee: Sahil Takiar
> Attachments: HIVE-15546.1.patch, HIVE-15546.2.patch
>
>
> When running on blobstores (like S3) where metadata operations (like
> listStatus) are costly, Utilities.getInputPaths() can add significant
> overhead when setting up the input paths for an MR / Spark / Tez job.
> The method performs a listStatus on all input paths in order to check if the
> path is empty. If the path is empty, a dummy file is created for the given
> partition. This is all done sequentially. This can be really slow when there
> are a lot of empty partitions. Even when all partitions have input data, this
> can take a long time.
> We should either:
> (1) Just remove the logic to check if each input path is empty, and handle
> any edge cases accordingly.
> (2) Multi-thread the listStatus calls
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