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Posted to issues@spark.apache.org by "Apache Spark (Jira)" <ji...@apache.org> on 2020/09/08 09:38:00 UTC
[jira] [Commented] (SPARK-32820) Remove redundant shuffle exchanges
inserted by EnsureRequirements
[ https://issues.apache.org/jira/browse/SPARK-32820?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17192081#comment-17192081 ]
Apache Spark commented on SPARK-32820:
--------------------------------------
User 'sarutak' has created a pull request for this issue:
https://github.com/apache/spark/pull/29677
> Remove redundant shuffle exchanges inserted by EnsureRequirements
> -----------------------------------------------------------------
>
> Key: SPARK-32820
> URL: https://issues.apache.org/jira/browse/SPARK-32820
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 3.1.0
> Reporter: Kousuke Saruta
> Assignee: Kousuke Saruta
> Priority: Major
>
> Redundant repartition operations are removed by CollapseRepartition rule but EnsureRequirements can insert another HashPartitioning or RangePartitioning immediately after the repartition, leading adjacent ShuffleExchanges will be in the physical plan.
>
> {code:java}
> val ordered = spark.range(1, 100).repartitionByRange(10, $"id".desc).orderBy($"id")
> ordered.explain(true)
> ...
> == Physical Plan ==
> *(2) Sort [id#0L ASC NULLS FIRST], true, 0
> +- Exchange rangepartitioning(id#0L ASC NULLS FIRST, 200), true, [id=#15]
> +- Exchange rangepartitioning(id#0L DESC NULLS LAST, 10), false, [id=#14]
> +- *(1) Range (1, 100, step=1, splits=12){code}
> {code:java}
> spark.conf.set("spark.sql.autoBroadcastJoinThreshold", 0)
> val left = Seq(1,2,3).toDF.repartition(10, $"value")
> val right = Seq(1,2,3).toDF
> val joined = left.join(right, left("value") + 1 === right("value")
> joined.explain(true)
> ...
> == Physical Plan ==
> *(3) SortMergeJoin [(value#7 + 1)], [value#12], Inner
> :- *(1) Sort [(value#7 + 1) ASC NULLS FIRST], false, 0
> : +- Exchange hashpartitioning((value#7 + 1), 200), true, [id=#67]
> : +- Exchange hashpartitioning(value#7, 10), false, [id=#63]
> : +- LocalTableScan [value#7]
> +- *(2) Sort [value#12 ASC NULLS FIRST], false, 0
> +- Exchange hashpartitioning(value#12, 200), true, [id=#68]
> +- LocalTableScan [value#12]{code}
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