Github user hequn8128 commented on a diff in the pull request: https://github.com/apache/flink/pull/5555#discussion_r170577575 --- 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)) + new PojoTypeInfo[DistinctAccumulator[E, ACC]](clazz, pojoFields) --- End diff -- Currently, `MapView` and `ListView` only supported at first level of accumulators of Pojo type. In other words, if realAcc also contains MapView, exceptions will be thrown. You can reproduce this exception by creating a test with `org.apache.flink.table.runtime.utils.JavaUserDefinedAggFunctions.CountDistinct(DISTINCT a)`.
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