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https://issues.apache.org/jira/browse/FLINK-6888?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16067649#comment-16067649
]
ASF GitHub Bot commented on FLINK-6888:
---------------------------------------
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 ?
```
> Can not determine TypeInformation of ACC type of AggregateFunction when ACC
> is a Scala case/tuple class
> -------------------------------------------------------------------------------------------------------
>
> Key: FLINK-6888
> URL: https://issues.apache.org/jira/browse/FLINK-6888
> Project: Flink
> Issue Type: Bug
> Components: Table API & SQL
> Reporter: Jark Wu
> Assignee: Jark Wu
> Fix For: 1.4.0
>
>
> Currently the {{ACC}} TypeInformation of
> {{org.apache.flink.table.functions.AggregateFunction[T, ACC]}} is extracted
> using {{TypeInformation.of(Class)}}. When {{ACC}} is a Scala case class or
> tuple class, the TypeInformation will fall back to {{GenericType}} which
> result in bad performance when state de/serialization.
> I suggest to extract the ACC TypeInformation when called
> {{TableEnvironment.registerFunction()}}.
> Here is an example:
> {code}
> case class Accumulator(sum: Long, count: Long)
> class MyAgg extends AggregateFunction[Long, Accumulator] {
> //Overloaded accumulate method
> def accumulate(acc: Accumulator, value: Long): Unit = {
> }
> override def createAccumulator(): Accumulator = Accumulator(0, 0)
> override def getValue(accumulator: Accumulator): Long = 1
> }
> {code}
> The {{Accumulator}} will be recognized as {{GenericType<Accumulator>}}.
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