Github user viirya commented on a diff in the pull request:
https://github.com/apache/spark/pull/21034#discussion_r180602624
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -212,6 +213,96 @@ case class SortArray(base: Expression, ascendingOrder:
Expression)
override def prettyName: String = "sort_array"
}
+/**
+ * Returns a reversed string or an array with reverse order of elements.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(array) - Returns a reversed string or an array with
reverse order of elements.",
+ examples = """
+ Examples:
+ > SELECT _FUNC_('Spark SQL');
+ LQS krapS
+ > SELECT _FUNC_(array(2, 1, 4, 3));
+ [3, 4, 1, 2]
+ """,
+ since = "2.4.0")
+case class Reverse(child: Expression) extends UnaryExpression with
ImplicitCastInputTypes {
+
+ // Input types are utilized by type coercion in ImplicitTypeCasts.
+ override def inputTypes: Seq[AbstractDataType] = Seq(StringType)
+
+ val allowedTypes = Seq(StringType, ArrayType)
+
+ override def dataType: DataType = child.dataType
+
+ lazy val elementType: DataType =
dataType.asInstanceOf[ArrayType].elementType
+
+ override def checkInputDataTypes(): TypeCheckResult = {
--- End diff --
I think you just make the `inputTypes` as `Seq(TypeCollection(StringType,
ArrayType))`. `ExpectsInputTypes` can check the types.
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