Github user kiszk commented on a diff in the pull request:
https://github.com/apache/spark/pull/21034#discussion_r180850179
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -212,6 +213,93 @@ 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 = "1.5.0",
+ note = "Reverse logic for arrays is available 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(TypeCollection(StringType, ArrayType))
+
+ override def dataType: DataType = child.dataType
+
+ lazy val elementType: DataType =
dataType.asInstanceOf[ArrayType].elementType
+
+ override def nullSafeEval(input: Any): Any = input match {
+ case a: ArrayData => new
GenericArrayData(a.toObjectArray(elementType).reverse)
+ case s: UTF8String => s.reverse()
+ }
+
+ override def doGenCode(ctx: CodegenContext, ev: ExprCode): ExprCode = {
+ nullSafeCodeGen(ctx, ev, c => dataType match {
+ case _: StringType => stringCodeGen(ev, c)
+ case _: ArrayType => arrayCodeGen(ctx, ev, c)
+ })
+ }
+
+ private def stringCodeGen(ev: ExprCode, childName: String): String = {
+ s"${ev.value} = ($childName).reverse();"
+ }
+
+ private def arrayCodeGen(ctx: CodegenContext, ev: ExprCode, childName:
String): String = {
+ val length = ctx.freshName("length")
+ val javaElementType = CodeGenerator.javaType(elementType)
+ val isPrimitiveType = CodeGenerator.isPrimitiveType(elementType)
+
+ val initialization = if (isPrimitiveType) {
+ s"$childName.copy()"
+ } else {
+ s"new ${classOf[GenericArrayData].getName()}(new Object[$length])"
+ }
+
+ val numberOfIterations = if (isPrimitiveType) s"$length / 2" else
length
+
+ val swapAssigments = if (isPrimitiveType) {
+ val setFunc = "set" + CodeGenerator.primitiveTypeName(elementType)
+ val getCall = (index: String) => CodeGenerator.getValue(ev.value,
elementType, index)
+ s"""|boolean isNullAtK = ${ev.value}.isNullAt(k);
+ |boolean isNullAtL = ${ev.value}.isNullAt(l);
+ |if(!isNullAtK) {
+ | $javaElementType el = ${getCall("k")};
+ | if(!isNullAtL) {
+ | ${ev.value}.$setFunc(k, ${getCall("l")});
+ | } else {
+ | ${ev.value}.setNullAt(k);
+ | }
+ | ${ev.value}.$setFunc(l, el);
+ |} else if (!isNullAtL) {
+ | ${ev.value}.$setFunc(k, ${getCall("l")});
+ | ${ev.value}.setNullAt(l);
+ |}""".stripMargin
+ } else {
+ s"${ev.value}.update(k, ${CodeGenerator.getValue(childName,
elementType, "l")});"
+ }
+
+ s"""
+ |final int $length = $childName.numElements();
--- End diff --
nit: more spaces
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