[jira] [Commented] (SPARK-18631) Avoid making data skew worse in ExchangeCoordinator

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-18631?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15706495#comment-15706495 ] 

Apache Spark commented on SPARK-18631:
--------------------------------------

User 'markhamstra' has created a pull request for this issue:
https://github.com/apache/spark/pull/16065

> Avoid making data skew worse in ExchangeCoordinator
> ---------------------------------------------------
>
>                 Key: SPARK-18631
>                 URL: https://issues.apache.org/jira/browse/SPARK-18631
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 1.6.3, 2.0.2, 2.1.0
>            Reporter: Mark Hamstra
>            Assignee: Mark Hamstra
>
> The logic to resize partitions in the ExchangeCoordinator is to not start a new partition until the targetPostShuffleInputSize is equalled or exceeded.  This can make data skew problems worse since a number of small partitions can first be combined as long as the combined size remains smaller than the targetPostShuffleInputSize, and then a large, data-skewed partition can be further combined, making it even bigger than it already was.
> It's a fairly simple to change the logic to create a new partition if adding a new piece would exceed the targetPostShuffleInputSize instead of only creating a new partition after the targetPostShuffleInputSize has already been exceeded.  This results in a few more partitions being created by the ExchangeCoordinator, but data skew problems are at least not made worse even though they are not made any better.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscribe@spark.apache.org
For additional commands, e-mail: issues-help@spark.apache.org