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From fhueske <...@git.apache.org>
Subject [GitHub] flink pull request #4105: [FLINK-6888] [table] Can not determine TypeInforma...
Date Fri, 16 Jun 2017 14:21:39 GMT
Github user fhueske commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4105#discussion_r122448432
  
    --- 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 --
    
    To be honest, I don't think it is a nice approach to add the acc type to the internal
representation of UDAGGs. It is not related to the logic of the function or required for the
optimization but rather an internal runtime aspect.
    
    An alternative could be to wrap the functions registered from Scala in a class that extends
the `AggregateFunction` interface and holds the original agg function and the acc type information
(exposed via the getAccumulatorType()` method). We would need to unwrap it before we translate
it. It's not a super nice solution either, but would probably require fewer changes.
    
    What do you think?


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