Github user wuchong commented on a diff in the pull request:
https://github.com/apache/flink/pull/4105#discussion_r124704209
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/utils/UserDefinedFunctionUtils.scala
---
@@ -320,12 +348,20 @@ object UserDefinedFunctionUtils {
} else if(extractedType != null) {
extractedType
} else {
- TypeExtractor
+ try {
+ TypeExtractor
--- End diff --
I think it is more safe than `TypeInformation.of(Any)`, because
`TypeInformation.of(Any)` can only works for non-generic types.
For example:
```
public class UDAF extends AggregateFunction[Tuple2<String, Long>, Long] {
public Long createAccumulator() {...}
public Tuple2<String, Long> getValue(Long acc) {...}
}
```
For the given UDAF, the return type is a generic type `Tuple2<String,
Long>`. We can't extract the return type from an instance of Tuple2, because
of Java type erasure. But we can extract it from the type hierarchy of UDAF
class.
Am I right, @twalthr ?
```
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