Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4105#discussion_r121625889
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/utils/UserDefinedFunctionUtils.scala
---
@@ -329,6 +337,41 @@ object UserDefinedFunctionUtils {
}
}
+
+ /**
+ * Internal method of AggregateFunction#getAccumulatorType() that does
some pre-checking
+ * and uses [[TypeExtractor]] as default return type inference.
+ */
+ def getAccumulatorTypeOfAggregateFunction(
+ aggregateFunction: AggregateFunction[_, _],
+ extractedType: TypeInformation[_] = null)
+ : TypeInformation[_] = {
+
+ val accType = try {
+ val method: Method =
aggregateFunction.getClass.getMethod("getAccumulatorType")
+ method.invoke(aggregateFunction).asInstanceOf[TypeInformation[_]]
+ } catch {
+ case _: NoSuchMethodException => null
+ case ite: Throwable => throw new TableException("Unexpected
exception:", ite)
+ }
+ if (accType != null) {
+ accType
+ } else if (extractedType != null) {
+ extractedType
+ } else {
+ val accumulator = aggregateFunction.createAccumulator()
+ try {
+ TypeInformation.of(accumulator.getClass)
--- End diff --
I think it's a good advice.
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