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https://issues.apache.org/jira/browse/SPARK-15441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15294807#comment-15294807
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Davies Liu commented on SPARK-15441:
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How to we represent a null in Dataset? If it's a row with all columns are
nulls, then we could transform a row with all columns are nulls into null,
right? In this case, the left side of the fourth row are nulls, it could be
null.
> dataset outer join seems to return incorrect result
> ---------------------------------------------------
>
> Key: SPARK-15441
> URL: https://issues.apache.org/jira/browse/SPARK-15441
> Project: Spark
> Issue Type: Bug
> Components: sq;
> Reporter: Reynold Xin
> Priority: Critical
>
> See notebook
> https://databricks-prod-cloudfront.cloud.databricks.com/public/4027ec902e239c93eaaa8714f173bcfc/6122906529858466/2836020637783173/5382278320999420/latest.html
> {code}
> import org.apache.spark.sql.functions
> val left = List(("a", 1), ("a", 2), ("b", 3), ("c", 4)).toDS()
> val right = List(("a", "x"), ("b", "y"), ("d", "z")).toDS()
> // The last row _1 should be null, rather than (null, -1)
> left.toDF("k", "v").as[(String, Int)].alias("left")
> .joinWith(right.toDF("k", "u").as[(String, String)].alias("right"),
> functions.col("left.k") === functions.col("right.k"), "right_outer")
> .show()
> {code}
> The returned result currently is
> {code}
> +---------+-----+
> | _1| _2|
> +---------+-----+
> | (a,2)|(a,x)|
> | (a,1)|(a,x)|
> | (b,3)|(b,y)|
> |(null,-1)|(d,z)|
> +---------+-----+
> {code}
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