Github user sunjincheng121 commented on a diff in the pull request:
https://github.com/apache/flink/pull/4556#discussion_r137142537
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/functions/aggfunctions/FirstValueAggFunctionWithRetract.scala
---
@@ -0,0 +1,121 @@
+/*
+ * 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.math.BigDecimal
+import java.util.{ArrayList => JArray, List => JList}
+
+import org.apache.flink.api.common.typeinfo.{BasicTypeInfo,
TypeInformation}
+import org.apache.flink.api.java.tuple.{Tuple1 => JTuple1}
+import org.apache.flink.api.java.typeutils.TupleTypeInfo
+import org.apache.flink.table.functions.AggregateFunction
+
+/** The initial accumulator for first value with retraction aggregate
function */
+class FirstValueWithRetractAccumulator[T] extends JTuple1[JList[T]]
--- End diff --
FLINK-7206 is done, I'll using `DataView` for improve the implementation.
---
