Github user hequn8128 commented on a diff in the pull request:
https://github.com/apache/flink/pull/5555#discussion_r170577531
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/DistinctAggDelegateFunction.scala
---
@@ -0,0 +1,122 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements. See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership. The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.functions.aggfunctions
+
+import java.util
+
+import org.apache.flink.api.common.typeinfo.{BasicTypeInfo,
TypeInformation}
+import org.apache.flink.api.java.typeutils.{PojoField, PojoTypeInfo}
+import org.apache.flink.table.api.dataview.MapView
+import org.apache.flink.table.dataview.MapViewTypeInfo
+import org.apache.flink.table.functions.AggregateFunction
+
+class DistinctAccumulator[E, ACC] (var mapView: MapView[E, Integer], var
realAcc: ACC) {
+ def this() {
+ this(null, null.asInstanceOf[ACC])
+ }
+
+ def getRealAcc: ACC = realAcc
+
+ def canEqual(a: Any): Boolean = a.isInstanceOf[DistinctAccumulator[E,
ACC]]
+
+ override def equals(that: Any): Boolean =
+ that match {
+ case that: DistinctAccumulator[E, ACC] => that.canEqual(this) &&
+ this.mapView == that.mapView
+ case _ => false
+ }
+
+}
+
+class DistinctAggDelegateFunction[E, ACC](elementTypeInfo:
TypeInformation[_],
+ var realAgg:
AggregateFunction[_, ACC])
+ extends AggregateFunction[util.Map[E, Integer], DistinctAccumulator[E,
ACC]] {
+
+ def getRealAgg: AggregateFunction[_, ACC] = realAgg
+
+ override def createAccumulator(): DistinctAccumulator[E, ACC] = {
+ new DistinctAccumulator[E, ACC](
+ new MapView[E, Integer](
+ elementTypeInfo.asInstanceOf[TypeInformation[E]],
+ BasicTypeInfo.INT_TYPE_INFO),
+ realAgg.createAccumulator())
+ }
+
+ def accumulate(acc: DistinctAccumulator[E, ACC], element: E): Boolean = {
+ if (element != null) {
+ if (acc.mapView.contains(element)) {
+ acc.mapView.put(element, acc.mapView.get(element) + 1)
+ false
+ } else {
+ acc.mapView.put(element, 1)
+ true
+ }
+ } else {
+ false
+ }
+ }
+
+ def accumulate(acc: DistinctAccumulator[E, ACC], element: E, count:
Int): Boolean = {
+ if (element != null) {
+ if (acc.mapView.contains(element)) {
+ acc.mapView.put(element, acc.mapView.get(element) + count)
+ false
+ } else {
+ acc.mapView.put(element, count)
+ true
+ }
+ } else {
+ false
+ }
+ }
+
+ def retract(acc: DistinctAccumulator[E, ACC], element: E): Boolean = {
+ if (element != null) {
+ val count = acc.mapView.get(element)
+ if (count == 1) {
+ acc.mapView.remove(element)
+ true
+ } else {
+ acc.mapView.put(element, count - 1)
+ false
+ }
+ } else {
+ false
+ }
+ }
+
+ def resetAccumulator(acc: DistinctAccumulator[E, ACC]): Unit = {
+ acc.mapView.clear()
+ }
+
+ override def getValue(acc: DistinctAccumulator[E, ACC]): util.Map[E,
Integer] = {
+ acc.mapView.map
+ }
+
+ override def getAccumulatorType: TypeInformation[DistinctAccumulator[E,
ACC]] = {
+ val clazz = classOf[DistinctAccumulator[E, ACC]]
+ val pojoFields = new util.ArrayList[PojoField]
+ pojoFields.add(new PojoField(clazz.getDeclaredField("mapView"),
+ new MapViewTypeInfo[E, Integer](
+ elementTypeInfo.asInstanceOf[TypeInformation[E]],
BasicTypeInfo.INT_TYPE_INFO)))
+ pojoFields.add(new PojoField(clazz.getDeclaredField("realAcc"),
+ realAgg.getAccumulatorType))
--- End diff --
`getAccumulatorType ` may return null if has not been overrided. In this
case, accumulator type should be inferred. see
`getAccumulatorTypeOfAggregateFunction()` in `UserDefinedFunctionUtils`.
---
