Github user ueshin commented on a diff in the pull request:
https://github.com/apache/spark/pull/21040#discussion_r182701319
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -287,3 +287,101 @@ case class ArrayContains(left: Expression, right:
Expression)
override def prettyName: String = "array_contains"
}
+
+
+/**
+ * Slices an array according to the requested start index and length
+ */
+// scalastyle:off line.size.limit
+@ExpressionDescription(
+ usage = "_FUNC_(a1, a2) - Subsets array x starting from index start (or
starting from the end if start is negative) with the specified length.",
+ examples = """
+ Examples:
+ > SELECT _FUNC_(array(1, 2, 3, 4), 2, 2);
+ [2,3]
+ > SELECT _FUNC_(array(1, 2, 3, 4), -2, 2);
+ [3,4]
+ """, since = "2.4.0")
+// scalastyle:on line.size.limit
+case class Slice(x: Expression, start: Expression, length: Expression)
+ extends TernaryExpression with ImplicitCastInputTypes {
+
+ override def dataType: DataType = x.dataType
+
+ override def inputTypes: Seq[AbstractDataType] = Seq(ArrayType,
IntegerType, IntegerType)
+
+ override def nullable: Boolean = children.exists(_.nullable)
+
+ override def foldable: Boolean = children.forall(_.foldable)
--- End diff --
We don't need `nullable` and `foldable` here because these are the same as
defined in `TernaryExpression`.
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