[GitHub] fhueske commented on a change in pull request #6521: [FLINK-5315][table] Adding support for distinct operation for table API on DataStream

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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_r217364366
 
 

 ##########
 File path: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/expressions/aggregations.scala
 ##########
 @@ -52,12 +54,48 @@ abstract sealed class Aggregation extends Expression {
 
 }
 
+case class DistinctAgg(child: Expression) extends Aggregation {
+
+  private[flink] def distinct: Expression = DistinctAgg(child)
+
+  override private[flink] def resultType: TypeInformation[_] = child.resultType
+
+  override private[flink] def validateInput(): ValidationResult = {
+    super.validateInput()
+    child match {
+      case agg: Aggregation =>
+        child.validateInput()
+      case _ =>
+        ValidationFailure(s"Distinct modifier cannot be applied to $child! " +
+          s"It can only be applied to an aggregation expression, for example, " +
+          s"'a.count.distinct which is equivalent with COUNT(DISTINCT a).")
+    }
+  }
+
+  override private[flink] def toAggCall(
+      name: String, isDistinct: Boolean = true)(implicit relBuilder: RelBuilder) = {
+    child.asInstanceOf[Aggregation].toAggCall(name, isDistinct = true)
+  }
+
+  override private[flink] def getSqlAggFunction()(implicit relBuilder: RelBuilder) = {
+    child.asInstanceOf[Aggregation].getSqlAggFunction()
+  }
+
+  override private[flink] def children = Seq(child)
+}
+
 case class Sum(child: Expression) extends Aggregation {
   override private[flink] def children: Seq[Expression] = Seq(child)
   override def toString = s"sum($child)"
 
-  override private[flink] def toAggCall(name: String)(implicit relBuilder: RelBuilder): AggCall = {
-    relBuilder.aggregateCall(SqlStdOperatorTable.SUM, false, false, null, name, child.toRexNode)
+  override private[flink] def toAggCall(
+      name: String, isDistinct: Boolean = false)(implicit relBuilder: RelBuilder): AggCall = {
+    relBuilder.aggregateCall(SqlStdOperatorTable.SUM,
 
 Review comment:
   Please move the first argument also in a new line (same for the other functions)

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