Github user HyukjinKwon commented on a diff in the pull request:
https://github.com/apache/spark/pull/20938#discussion_r179970006
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -287,3 +289,165 @@ case class ArrayContains(left: Expression, right:
Expression)
override def prettyName: String = "array_contains"
}
+
+/**
+ * Transforms an array of arrays into a single array.
+ */
+@ExpressionDescription(
+ usage = "_FUNC_(arrayOfArrays) - Transforms an array of arrays into a
single array.",
+ examples = """
+ Examples:
+ > SELECT _FUNC_(array(array(1, 2), array(3, 4));
+ [1,2,3,4]
+ """)
+case class Flatten(child: Expression) extends UnaryExpression {
+
+ override def nullable: Boolean = child.nullable || dataType.containsNull
+
+ override def dataType: ArrayType = {
+ child
+ .dataType.asInstanceOf[ArrayType]
+ .elementType.asInstanceOf[ArrayType]
+ }
+
+ override def checkInputDataTypes(): TypeCheckResult = {
+ if (
+ ArrayType.acceptsType(child.dataType) &&
+
ArrayType.acceptsType(child.dataType.asInstanceOf[ArrayType].elementType)
+ ) {
+ TypeCheckResult.TypeCheckSuccess
+ } else {
+ TypeCheckResult.TypeCheckFailure(
+ s"The argument should be an array of arrays, " +
+ s"but '${child.sql}' is of ${child.dataType.simpleString} type."
+ )
+ }
+ }
+
+ override def nullSafeEval(array: Any): Any = {
+ val elements = array.asInstanceOf[ArrayData].toObjectArray(dataType)
+
+ if (elements.contains(null)) {
+ null
+ } else {
+ val flattened = elements.flatMap(
+ _.asInstanceOf[ArrayData].toObjectArray(dataType.elementType)
+ )
+ new GenericArrayData(flattened)
+ }
+ }
+
+ override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ nullSafeCodeGen(ctx, ev, c => {
+ val code =
+ if (CodeGenerator.isPrimitiveType(dataType.elementType)) {
--- End diff --
very tiny nit: shall we move this line up?
```
val code = if (Code...
```
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