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From "Jimmy Xiang (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HIVE-10302) Load small tables (for map join) in executor memory only once [Spark Branch]
Date Fri, 24 Apr 2015 18:37:38 GMT

     [ https://issues.apache.org/jira/browse/HIVE-10302?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jimmy Xiang updated HIVE-10302:
-------------------------------
    Attachment: HIVE-10302.4-spark.patch

Thanks a lot for the discussion and review. Yes, the spark related test failures are related.
It is because the loaded small tables are cleared after the map join. So the table container
is empty in the cache.  Attached v4 that doesn't clear the small tables in case it is spark
and dedicated cluster, when the small tables are cached.

> 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: spark-branch
>
>         Attachments: 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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