Github user rxin commented on a diff in the pull request:
https://github.com/apache/spark/pull/6616#discussion_r31696920
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/DataFrame.scala ---
@@ -395,22 +395,35 @@ class DataFrame private[sql](
* @since 1.4.0
*/
def join(right: DataFrame, usingColumn: String): DataFrame = {
+ join(right, Seq(usingColumn))
+ }
+
+ def join(right: DataFrame, usingColumns: Seq[String]): DataFrame = {
// Analyze the self join. The assumption is that the analyzer will
disambiguate left vs right
// by creating a new instance for one of the branch.
val joined = sqlContext.executePlan(
Join(logicalPlan, right.logicalPlan, joinType = Inner,
None)).analyzed.asInstanceOf[Join]
- // Project only one of the join column.
- val joinedCol = joined.right.resolve(usingColumn)
+ // Project only one of the join columns.
+ val joinedCols = usingColumns.map(col => joined.right.resolve(col))
+ val condition = usingColumns.map { col =>
+ catalyst.expressions.EqualTo(joined.left.resolve(col),
joined.right.resolve(col))
+ }.foldLeft[Option[catalyst.expressions.BinaryExpression]](None) {
(opt, eqTo) =>
--- End diff --
this can be simplifed into a reduceOption right?
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