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From wuchong <...@git.apache.org>
Subject [GitHub] flink pull request #4105: [FLINK-6888] [table] Can not determine TypeInforma...
Date Tue, 20 Jun 2017 12:48:34 GMT
Github user wuchong commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4105#discussion_r122964903
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/TableEnvironment.scala
---
    @@ -358,20 +358,27 @@ abstract class TableEnvironment(val config: TableConfig) {
         * Registers an [[AggregateFunction]] under a unique name. Replaces already existing
         * user-defined functions under this name.
         */
    -  private[flink] def registerAggregateFunctionInternal[T: TypeInformation, ACC](
    +  private[flink] def registerAggregateFunctionInternal[T: TypeInformation, ACC: TypeInformation](
           name: String, function: AggregateFunction[T, ACC]): Unit = {
         // check if class not Scala object
         checkNotSingleton(function.getClass)
         // check if class could be instantiated
         checkForInstantiation(function.getClass)
     
    -    val typeInfo: TypeInformation[_] = implicitly[TypeInformation[T]]
    +    val resultTypeInfo: TypeInformation[_] = implicitly[TypeInformation[T]]
    +    val accTypeInfo: TypeInformation[_] = implicitly[TypeInformation[ACC]]
     
         // register in Table API
         functionCatalog.registerFunction(name, function.getClass)
     
         // register in SQL API
    -    val sqlFunctions = createAggregateSqlFunction(name, function, typeInfo, typeFactory)
    +    val sqlFunctions = createAggregateSqlFunction(
    --- End diff --
    
    @fhueske thanks for your explanation. I tried to wrap the UDAGG in an `AggregateFunctionWrapper`,
but find that it is not an easy way. Because I can't override the user-defined contract methods,
such as `accumulate`, `retract`, `merge`. And in code generation, we generate the acc type
class depend on `createAccumulator` method return type, but the return type of `createAccumulator`
of `AggregateFunctionWrapper` can only be `Any` which will result in error.
    
    In addition, I plan to support composite result type for UDAGG. This also need the return
type not only to be known to Calcite for semantic validation but also to be known for code
generation.


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