Github user kiszk commented on a diff in the pull request: https://github.com/apache/spark/pull/21053#discussion_r181793795 --- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala --- @@ -287,3 +287,106 @@ case class ArrayContains(left: Expression, right: Expression) override def prettyName: String = "array_contains" } + +/** + * Returns the value of index `right` in Array `left` or the value for key `right` in Map `left`. + */ +@ExpressionDescription( + usage = """ + _FUNC_(array, index) - Returns element of array at given index. If index < 0, accesses elements + from the last to the first. + + _FUNC_(map, key) - Returns value for given key, or NULL if the key is not contained in the map + """, + examples = """ + Examples: + > SELECT _FUNC_(array(1, 2, 3), 2); + 2 + > SELECT _FUNC_(map(1, 'a', 2, 'b'), 2); + "b" + """, + since = "2.4.0") +case class ElementAt(left: Expression, right: Expression) extends GetMapValueUtil { + + override def dataType: DataType = left.dataType match { + case _: ArrayType => left.dataType.asInstanceOf[ArrayType].elementType + case _: MapType => left.dataType.asInstanceOf[MapType].valueType + } + + override def inputTypes: Seq[AbstractDataType] = { + Seq(TypeCollection(ArrayType, MapType), + left.dataType match { + case _: ArrayType => IntegerType + case _: MapType => left.dataType.asInstanceOf[MapType].keyType + } + ) + } + + override def nullable: Boolean = true --- End diff -- year, may depend on `right` value, too.
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