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

["Enrico Minack (Jira)" <ji...@apache.org>]

Enrico Minack created SPARK-30957:
-------------------------------------

             Summary: 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


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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