Github user mn-mikke commented on a diff in the pull request:
https://github.com/apache/spark/pull/20858#discussion_r177419513
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -287,3 +289,152 @@ case class ArrayContains(left: Expression, right:
Expression)
override def prettyName: String = "array_contains"
}
+
+/**
+ * Concatenates multiple arrays into one.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(expr, ...) - Concatenates multiple arrays into one.",
+ examples = """
+ Examples:
+ > SELECT _FUNC_(array(1, 2, 3), array(4, 5), array(6));
+ [1,2,3,4,5,6]
+ """)
+case class ConcatArrays(children: Seq[Expression]) extends Expression with
NullSafeEvaluation {
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ val arrayCheck = checkInputDataTypesAreArrays
+ if(arrayCheck.isFailure) arrayCheck
+ else TypeUtils.checkForSameTypeInputExpr(children.map(_.dataType),
s"function $prettyName")
+ }
+
+ private def checkInputDataTypesAreArrays(): TypeCheckResult =
+ {
+ val mismatches = children.zipWithIndex.collect {
+ case (child, idx) if !ArrayType.acceptsType(child.dataType) =>
+ s"argument ${idx + 1} has to be ${ArrayType.simpleString} type, " +
+ s"however, '${child.sql}' is of ${child.dataType.simpleString}
type."
+ }
+
+ if (mismatches.isEmpty) {
+ TypeCheckResult.TypeCheckSuccess
+ } else {
+ TypeCheckResult.TypeCheckFailure(mismatches.mkString(" "))
+ }
+ }
+
+ override def dataType: ArrayType =
+ children
+ .headOption.map(_.dataType.asInstanceOf[ArrayType])
+ .getOrElse(ArrayType.defaultConcreteType.asInstanceOf[ArrayType])
--- End diff --
Ok, changing to return type `array<string>` when no children are provided.
Also I've created the jira ticket
[SPARK-23798](https://issues.apache.org/jira/browse/SPARK-23798) since I don't
see any reason why it couldn't return a default concrete type in this case.
Hope I don't miss anything.
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