Github user kiszk commented on a diff in the pull request:
https://github.com/apache/spark/pull/21802#discussion_r204270437
--- Diff:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/collectionOperations.scala
---
@@ -1184,6 +1186,137 @@ case class ArraySort(child: Expression) extends
UnaryExpression with ArraySortLi
override def prettyName: String = "array_sort"
}
+/**
+ * Returns a random permutation of the given array.
+ *
+ * This implementation uses the modern version of Fisher-Yates algorithm.
+ * Reference:
https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#Modern_method
--- End diff --
In the latest commit, "inside-out" looks simpler without swapping (using
just an assignment).
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