[jira] [Commented] (SPARK-30957) Null-safe variant of Dataset.join(Dataset[_], Seq[String])

["Hyukjin Kwon (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-30957?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17049890#comment-17049890 ] 

Hyukjin Kwon commented on SPARK-30957:
--------------------------------------

I currently don't think this is particularly useful. We don't have method likes joinSelf or joinRange which is too verbose. The workarounds look easy enough.

> Null-safe variant of Dataset.join(Dataset[_], Seq[String])
> ----------------------------------------------------------
>
>                 Key: SPARK-30957
>                 URL: https://issues.apache.org/jira/browse/SPARK-30957
>             Project: Spark
>          Issue Type: Improvement
>          Components: SQL
>    Affects Versions: 3.1.0
>            Reporter: Enrico Minack
>            Priority: Major
>
> The {{Dataset.join(Dataset, Seq[String])}} method provides extra convenience over {{Dataset.join(Dataset, joinExprs: Column)}} as it does not duplicate the join columns {{Seq[String]}} in the result {{DataFrame}}. Those columns are compared with {{===}}. When those join columns need to be compared null-safe with {{<=>}}, the join condition becomes very verbose and requires extra {{drop}} operations:
> {code:java}
> df1.join(df2, df1("a") <=> df2("a") && df1("b") <=> df2("b")).drop(df2("a")).drop(df2("b")).show()
> {code}
> Elegant would be the following null-safe join operation:
> {code:java}
> df1.joinNullSafe(df2, joinColumns)
> {code}
> Possible namings:
>  - {{Dataset.joinNullSafe(Dataset[_], Seq[String])}}
>  - {{Dataset.joinWithNulls(Dataset[_], Seq[String])}}
>  - {{Dataset.join(Dataset[_], Seq[String], <=>)}}
> *I am happy to provide a PR if this Dataset API extension is appreciated.*
> This request has been sent to the Apache Spark user and [dev|http://apache-spark-developers-list.1001551.n3.nabble.com/Fwd-dataframe-null-safe-joins-given-a-list-of-columns-tt28842.html] mailing list by Marcelo Valle.



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