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https://issues.apache.org/jira/browse/FLINK-5767?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15880286#comment-15880286
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ASF GitHub Bot commented on FLINK-5767:
---------------------------------------
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.
> New aggregate function interface and built-in aggregate functions
> -----------------------------------------------------------------
>
> Key: FLINK-5767
> URL: https://issues.apache.org/jira/browse/FLINK-5767
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Shaoxuan Wang
> Assignee: Shaoxuan Wang
>
> Add a new aggregate function interface. This includes implementing the
> aggregate interface, migrating the existing aggregation functions to this
> interface, and adding the unit tests for these functions.
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