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https://issues.apache.org/jira/browse/SPARK-37829?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17706591#comment-17706591
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Jason Xu commented on SPARK-37829:
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Our company encountered this issue during our migration from Spark 2.4 to 3.
This issue may cause data correctness issues in our pipeline, as null is used
to determine whether there is a matching row in a DataFrame outer join.
To unblock the migration, we would like to backport the fixing patch from
upstream. However, I noticed that the pull requests above have been closed due
to inactivity.
[~cdegroc], are you planning to resume this work?
By the way, I'm happy to help in any way!
> An outer-join using joinWith on DataFrames returns Rows with null fields
> instead of null values
> -----------------------------------------------------------------------------------------------
>
> Key: SPARK-37829
> URL: https://issues.apache.org/jira/browse/SPARK-37829
> Project: Spark
> Issue Type: Bug
> Components: SQL
> Affects Versions: 3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.1.0, 3.1.1, 3.1.2, 3.2.0
> Reporter: Clément de Groc
> Priority: Major
>
> Doing an outer-join using {{joinWith}} on {{{}DataFrame{}}}s used to return
> missing values as {{null}} in Spark 2.4.8, but returns them as {{Rows}} with
> {{null}} values in Spark 3+.
> The issue can be reproduced with [the following
> test|https://github.com/cdegroc/spark/commit/79f4d6a1ec6c69b10b72dbc8f92ab6490d5ef5e5]
> that succeeds on Spark 2.4.8 but fails starting from Spark 3.0.0.
> The problem only arises when working with DataFrames: Datasets of case
> classes work as expected as demonstrated by [this other
> test|https://github.com/apache/spark/blob/v3.0.0/sql/core/src/test/scala/org/apache/spark/sql/DatasetSuite.scala#L1200-L1223].
> I couldn't find an explanation for this change in the Migration guide so I'm
> assuming this is a bug.
> A {{git bisect}} pointed me to [that
> commit|https://github.com/apache/spark/commit/cd92f25be5a221e0d4618925f7bc9dfd3bb8cb59].
> Reverting the commit solves the problem.
> A similar solution, but without reverting, is shown
> [here|https://github.com/cdegroc/spark/commit/684c675bf070876a475a9b225f6c2f92edce4c8a].
> Happy to help if you think of another approach / can provide some guidance.
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