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https://issues.apache.org/jira/browse/FLINK-7206?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16105185#comment-16105185
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ASF GitHub Bot commented on FLINK-7206:
---------------------------------------
Github user fhueske commented on a diff in the pull request:
https://github.com/apache/flink/pull/4355#discussion_r130057272
--- Diff:
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/dataview/MapView.scala
---
@@ -0,0 +1,184 @@
+/*
+ * 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.api.dataview
+
+import java.lang.{Iterable => JIterable}
+import java.util
+
+import org.apache.flink.api.common.typeinfo.{TypeInfo, TypeInformation}
+import org.apache.flink.table.dataview.MapViewTypeInfoFactory
+
+/**
+ * MapView encapsulates the operation of map.
+ *
+ * All methods in this class are not implemented, users do not need to
care about whether it is
+ * backed by Java HashMap or state backend. It will be replaced by a
{@link StateMapView} or a
+ * {@link HeapMapView}.
+ *
+ * <p>
+ * <b>NOTE:</b> Users are not recommended to extends this class.
+ * </p>
+ *
+ * Example:
+ * {{{
+ *
+ * public class MyAccum {
+ * public MapView<String, Integer> map;
+ * public long count;
+ * }
+ *
+ * public class MyAgg extends AggregateFunction<Long, MyAccum> {
+ *
+ * @Override
+ * public MyAccum createAccumulator() {
+ * MyAccum accum = new MyAccum();
+ * accum.map = new MapView<>(Types.STRING, Types.INT);
+ * accum.count = 0L;
+ * return accum;
+ * }
+ *
+ * //Overloaded accumulate method
+ * public void accumulate(MyAccum accumulator, String id) {
+ * try {
+ * if (!accumulator.map.contains(id)) {
+ * accumulator.map.put(id, 1);
+ * accumulator.count++;
+ * }
+ * } catch (Exception e) {
+ * e.printStackTrace();
+ * }
+ * }
+ *
+ * @Override
+ * public Long getValue(MyAccum accumulator) {
+ * return accumulator.count;
+ * }
+ * }
+ *
+ * }}}
+ *
+ * @param keyTypeInfo key type information
+ * @param valueTypeInfo value type information
+ * @tparam K key type
+ * @tparam V value type
+ */
+@TypeInfo(classOf[MapViewTypeInfoFactory[_, _]])
+class MapView[K, V](
--- End diff --
Most comments on `ListState` apply here as well.
> Implementation of DataView to support state access for UDAGG
> ------------------------------------------------------------
>
> Key: FLINK-7206
> URL: https://issues.apache.org/jira/browse/FLINK-7206
> Project: Flink
> Issue Type: Sub-task
> Components: Table API & SQL
> Reporter: Kaibo Zhou
> Assignee: Kaibo Zhou
>
> Implementation of MapView and ListView to support state access for UDAGG.
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