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Posted to issues@spark.apache.org by "Apache Spark (JIRA)" <ji...@apache.org> on 2018/09/06 04:53:00 UTC

[jira] [Assigned] (SPARK-25352) Perform ordered global limit when limit number is bigger than topKSortFallbackThreshold

     [ https://issues.apache.org/jira/browse/SPARK-25352?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Apache Spark reassigned SPARK-25352:
------------------------------------

    Assignee: Apache Spark

> Perform ordered global limit when limit number is bigger than topKSortFallbackThreshold
> ---------------------------------------------------------------------------------------
>
>                 Key: SPARK-25352
>                 URL: https://issues.apache.org/jira/browse/SPARK-25352
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.4.0
>            Reporter: Liang-Chi Hsieh
>            Assignee: Apache Spark
>            Priority: Major
>
> We have optimization on global limit to evenly distribute limit rows across all partitions. This optimization doesn't work for ordered results.
> For a query ending with sort + limit, in most cases it is performed by `TakeOrderedAndProjectExec`.
> But if limit number is bigger than `SQLConf.TOP_K_SORT_FALLBACK_THRESHOLD`, global limit will be used. At this moment, we need to do ordered global limit.



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