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From "Stavros Kontopoulos (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-17959) spark.sql.join.preferSortMergeJoin has no effect for simple join due to calculated size of LogicalRdd
Date Tue, 25 Oct 2016 09:44:58 GMT

    [ https://issues.apache.org/jira/browse/SPARK-17959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15604810#comment-15604810
] 

Stavros Kontopoulos commented on SPARK-17959:
---------------------------------------------

[~srowen]What do you think? I was not sure who I should ping this time.

> spark.sql.join.preferSortMergeJoin has no effect for simple join due to calculated size
of LogicalRdd
> -----------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-17959
>                 URL: https://issues.apache.org/jira/browse/SPARK-17959
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.0.1
>            Reporter: Stavros Kontopoulos
>
> Example code:   
> val df = spark.sparkContext.parallelize(List(("A", 10, "dss@s1"), ("A", 20, "dss@s2"),
>       ("B", 1, "dss@qqa"), ("B", 2, "dss@qqb"))).toDF("Group", "Amount", "Email")
>     df.as("a").join(df.as("b"))
>       .where($"a.Group" === $"b.Group")
>       .explain()
> I always get the SortMerge strategy (never shuffle hash join) even if i set spark.sql.join.preferSortMergeJoin
to false since:
> sinzeInBytes = 2^63-1
> https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/ExistingRDD.scala#L101
> and thus:
> condition here: https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala#L127
> is always false...
> I think this shouldnt be the case my df has a specifc size and number of partitions (200
which is btw far from optimal)...



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