Github user dongjoon-hyun commented on a diff in the pull request: https://github.com/apache/spark/pull/13967#discussion_r69176019 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala --- @@ -44,6 +44,58 @@ case class Size(child: Expression) extends UnaryExpression with ExpectsInputType } /** + * Returns an unordered array containing the keys of the map. + */ +@ExpressionDescription( + usage = "_FUNC_(map) - Returns an unordered array containing the keys of the map.", + extended = " > SELECT _FUNC_(map(1, 'a', 2, 'b'));\n [1,2]") +case class MapKeys(child: Expression) + extends UnaryExpression with ExpectsInputTypes { + + override def inputTypes: Seq[AbstractDataType] = Seq(MapType) + + override def dataType: DataType = ArrayType(child.dataType.asInstanceOf[MapType].keyType) + + override def foldable: Boolean = child.foldable --- End diff -- Yep.
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