Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/5555#discussion_r184040192
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/DistinctAccumulator.scala
---
@@ -0,0 +1,106 @@
+/*
+ * 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.lang.{Long => JLong}
+import java.lang.{Iterable => JIterable}
+import java.util.{Map => JMap}
+
+import org.apache.flink.table.api.dataview.MapView
+
+/**
+ * The base class for accumulator wrapper when applying distinct
aggregation.
+ * @param realAcc the actual accumulator which gets invoke after distinct
filter.
+ * @param mapView the [[MapView]] element used to store the distinct
filter hash map.
+ * @tparam E the element type for the distinct filter hash map.
+ * @tparam ACC the accumulator type for the realAcc.
+ */
+class DistinctAccumulator[E, ACC](var realAcc: ACC, var mapView:
MapView[E, JLong]) {
--- End diff --
rename `mapView` to `distinctValueMap`?
---
