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From "Kevin Wilfong (JIRA)" <>
Subject [jira] [Updated] (HIVE-3302) Race condition in query plan for merging at the end of a query
Date Thu, 26 Jul 2012 21:42:34 GMT


Kevin Wilfong updated HIVE-3302:

    Status: Patch Available  (was: Open)
> Race condition in query plan for merging at the end of a query
> --------------------------------------------------------------
>                 Key: HIVE-3302
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: Query Processor
>    Affects Versions: 0.10.0
>            Reporter: Kevin Wilfong
>            Assignee: Kevin Wilfong
>            Priority: Critical
>         Attachments: HIVE-3302.1.patch.txt
> In the query plan that's used to merge files at the end of a query, the dependency tree
looks something like:
>                    MoveTask(1)
>                   /           \
> ...ConditionalTask             MoveTask(2)...
>                   \           /
>                    MergeTask
> Here MoveTask(1) moves the partition data to a temporary location, and MoveTask(2) moves
it to the final location.
> However if there are dynamic partitions generated and some of these partitions are merged
and others are moved, the dependency tree is changed at runtime to:
> ...ConditionalTask           MoveTask(2)...
>                   \         /
>                    MergeTask
>                             \
>                              MoveTask(1)
> This produces a race condition between the two MoveTasks where if MoveTask(2) runs before
MoveTask(1) the partitions moved by MoveTask(1) will get moved to an intermediate location
and never moved to the final location.  In this case those partitions are quietly lost.

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