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https://issues.apache.org/jira/browse/HIVE-7372?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14057246#comment-14057246
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Chengxiang Li commented on HIVE-7372:
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"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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