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https://issues.apache.org/jira/browse/HIVE-15114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15671167#comment-15671167
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Sergio Peña commented on HIVE-15114:
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[~stakiar] The conditional task created on the GenMapRedUtils class also
creates tasks for Spark or Tez. The MoveTask should be linked to any task
regardless the execution engine.
The .q tests added to the TestBlobstorecliDriver can be executed with any
engine as well, so nothing to change. However, I did not verify those tests
were running correctly on them. I will run them and verify they work.
> Remove extra MoveTask operators
> -------------------------------
>
> Key: HIVE-15114
> URL: https://issues.apache.org/jira/browse/HIVE-15114
> Project: Hive
> Issue Type: Sub-task
> Components: Hive
> Affects Versions: 2.1.0
> Reporter: Sahil Takiar
> Assignee: Sergio Peña
> Attachments: HIVE-15114.WIP.1.patch, HIVE-15114.WIP.2.patch
>
>
> When running simple insert queries (e.g. {{INSERT INTO TABLE ... VALUES
> ...}}) there an extraneous {{MoveTask}s is created.
> This is problematic when the scratch directory is on S3 since renames require
> copying the entire dataset.
> For simple queries (like the one above), there are two MoveTasks. The first
> one moves the output data from one file in the scratch directory to another
> file in the scratch directory. The second MoveTask moves the data from the
> scratch directory to its final table location.
> The first MoveTask should not be necessary. The goal of this JIRA it to
> remove it. This should help improve performance when running on S3.
> It seems that the first Move might be caused by a dependency resolution
> problem in the optimizer, where a dependent task doesn't get properly removed
> when the task it depends on is filtered by a condition resolver.
> A dummy {{MoveTask}} is added in the
> {{GenMapRedUtils.createMRWorkForMergingFiles}} method. This method creates a
> conditional task which launches a job to merge tasks at the end of the file.
> At the end of the conditional job there is a MoveTask.
> Even though Hive decides that the conditional merge job is no needed, it
> seems the MoveTask is still added to the plan.
> Seems this extra {{MoveTask}} may have been added intentionally. Not sure why
> yet. The {{ConditionalResolverMergeFiles}} says that one of three tasks will
> be returned: move task only, merge task only, merge task followed by a move
> task.
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