Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/3354#discussion_r102693258
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/MaxAggFunction.scala
---
@@ -28,8 +28,9 @@ import org.apache.flink.table.functions.{Accumulator,
AggregateFunction}
* @tparam T the type for the aggregation result
*/
abstract class MaxAggFunction[T](implicit ord: Ordering[T]) extends
AggregateFunction[T] {
+
/** The initial accumulator for Max aggregate function */
- class MaxAccumulator[T] extends Accumulator {
+ class MaxAccumulator[T] extends JTuple2[T, Boolean] with Accumulator {
var max: T = null.asInstanceOf[T]
--- End diff --
Instead of adding a field here, you need to provide default values in the
`createAccumulator` method. Note, `f0` and `f1` may not be null. Otherwise,
the tuple cannot be serialized.
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