Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/2919#discussion_r91111043
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/api/scala/table/expressionDsl.scala
---
@@ -454,6 +455,29 @@ trait ImplicitExpressionOperations {
* into a flat representation where every subtype is a separate field.
*/
def flatten() = Flattening(expr)
+
+ /**
+ * Accesses the element of an array based on an index (starting at 1).
+ *
+ * @param index position of the element (starting at 1)
+ * @return value of the element
+ */
+ def at(index: Expression) = ArrayElementAt(expr, index)
+
+ /**
+ * Returns the number of elements of an array.
+ *
+ * @return number of element
+ */
+ def cardinality() = ArrayCardinality(expr)
+
+ /**
+ * Returns the sole element of an array. Returns null if the collection
is empty.
+ * Throws an exception if the array has more than one element.
+ *
+ * @return first element of the array
--- End diff --
`the only element of an array with a single entry`?
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