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From "Sergey Shelukhin (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-10302) Load small tables (for map join) in executor memory only once [Spark Branch]
Date Mon, 01 Jun 2015 23:08:17 GMT

    [ https://issues.apache.org/jira/browse/HIVE-10302?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14568202#comment-14568202
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Sergey Shelukhin commented on HIVE-10302:
-----------------------------------------

Actually I wonder why you guys still work on routine jiras on the branch after the main merge.
Usually branch is reserved for major feature and abandoned after merge, unless there's some
other major feature with epic merge...

> Load small tables (for map join) in executor memory only once [Spark Branch]
> ----------------------------------------------------------------------------
>
>                 Key: HIVE-10302
>                 URL: https://issues.apache.org/jira/browse/HIVE-10302
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Jimmy Xiang
>            Assignee: Jimmy Xiang
>             Fix For: 1.3.0
>
>         Attachments: 10302.patch, HIVE-10302.2-spark.patch, HIVE-10302.3-spark.patch,
HIVE-10302.4-spark.patch, HIVE-10302.spark-1.patch
>
>
> Usually there are multiple cores in a Spark executor, and thus it's possible that multiple
map-join tasks can be running in the same executor (concurrently or sequentially). Currently,
each task will load its own copy of the small tables for map join into memory, ending up with
inefficiency. Ideally, we only load the small tables once and share them among the tasks running
in that executor.



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