Github user twalthr commented on a diff in the pull request:
https://github.com/apache/flink/pull/3809#discussion_r114541011
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/aggregations.scala
---
@@ -130,3 +142,63 @@ case class Avg(child: Expression) extends Aggregation {
new SqlAvgAggFunction(AVG)
}
}
+
+case class UDAGGFunctionCall(
+ aggregateFunction: AggregateFunction[_, _],
+ args: Seq[Expression])
+ extends Aggregation {
+
+ override private[flink] def children: Seq[Expression] = args
+
+ // Override makeCopy method in TreeNode, to produce vargars properly
+ override def makeCopy(args: Array[AnyRef]): this.type = {
+ if (args.length < 1) {
+ throw new TableException("Invalid constructor params")
+ }
+ val agg = args.head.asInstanceOf[AggregateFunction[_, _]]
+ val arg = args.last.asInstanceOf[Seq[Expression]]
+ new UDAGGFunctionCall(agg, arg).asInstanceOf[this.type]
+ }
+
+ override def resultType: TypeInformation[_] =
TypeExtractor.createTypeInfo(
--- End diff --
This is again very dangerous. Type extraction fails very often. We should
provide a `getResultType` in `AggregateFunction` that the user can implement.
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