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From "Chengxiang Li (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-7372) Select query gives unpredictable incorrect result when parallelism is greater than 1 [Spark Branch]
Date Thu, 10 Jul 2014 08:04:05 GMT

    [ https://issues.apache.org/jira/browse/HIVE-7372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14057246#comment-14057246
] 

Chengxiang Li commented on HIVE-7372:
-------------------------------------

"select count(*) from test" return 5 results as reducerCount is set to 5 in SparkClient hardhanded,
reduce parallelism should consider several factors, i change the default value to 1 temporary
for this POC workround.

> Select query gives unpredictable incorrect result when parallelism is greater than 1
[Spark Branch]
> ---------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-7372
>                 URL: https://issues.apache.org/jira/browse/HIVE-7372
>             Project: Hive
>          Issue Type: Bug
>          Components: Spark
>            Reporter: Xuefu Zhang
>            Assignee: Chengxiang Li
>         Attachments: HIVE-7372.patch
>
>
> In SparkClient.java, if the following property is set, unpredictable, incorrect result
may be observed.
> {code}
>     sparkConf.set("spark.default.parallelism", "1");
> {code}
> It's suspected that there are some concurrency issues, as Spark may process multiple
datasets in a single JVM when parallelism is greater than 1 in order to use multiple cores.



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