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Subject [GitHub] fhueske commented on a change in pull request #6521: [FLINK-5315][table] Adding support for distinct operation for table API on DataStream
Date Mon, 20 Aug 2018 14:02:30 GMT
fhueske commented on a change in pull request #6521: [FLINK-5315][table] Adding support for
distinct operation for table API on DataStream
URL: https://github.com/apache/flink/pull/6521#discussion_r211270531
 
 

 ##########
 File path: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/AggregateFunction.scala
 ##########
 @@ -136,4 +138,12 @@ abstract class AggregateFunction[T, ACC] extends UserDefinedFunction
{
     *         accumulator type should be automatically inferred.
     */
   def getAccumulatorType: TypeInformation[ACC] = null
+
+  /**
+    * Returns an aggregation function that requires distinct accumulator.
+    * @return distinct aggregate version of the [[AggregateFunction]].
+    */
+  private[flink] def distinct: DistinctAggregateFunction[T, ACC] = DistinctAggregateFunction(this)
 }
+
+private[flink] case class DistinctAggregateFunction[T, ACC](aggFunction: AggregateFunction[T,
ACC])
 
 Review comment:
   Extend this class to
   
   ```
   private[flink] case class DistinctAggregateFunction[T: TypeInformation, ACC: TypeInformation]
       (aggFunction: AggregateFunction[T, ACC]) {
   
     private[flink] def distinct(params: Expression*): Expression = {
       val resultTypeInfo: TypeInformation[_] = getResultTypeOfAggregateFunction(
         aggFunction,
         implicitly[TypeInformation[T]])
   
       val accTypeInfo: TypeInformation[_] = getAccumulatorTypeOfAggregateFunction(
         aggFunction,
         implicitly[TypeInformation[ACC]])
   
       DistinctAgg(
         AggFunctionCall(aggFunction, resultTypeInfo, accTypeInfo, params))
     }
   }
   ```
   
   and move it to a separate file.

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