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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_r130655818 --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/api/dataview/ListView.scala --- @@ -0,0 +1,103 @@ +/* + * 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 org.apache.flink.api.common.typeinfo.{TypeInfo, TypeInformation} +import org.apache.flink.table.dataview.ListViewTypeInfoFactory + +/** + * ListView encapsulates the operation of list. + * + * All methods in this class are not implemented, users do not need to care about whether it is + * backed by Java ArrayList or state backend. It will be replaced by a {@link StateListView} or a + * {@link HeapListView}. + * + * <p> + * <b>NOTE:</b> Users are not recommended to extends this class. + * </p> + * + * Example: + * {{{ + * + * public class MyAccum { + * public ListView<String> list; + * public long count; + * } + * + * public class MyAgg extends AggregateFunction<Long, MyAccum> { + * + * @Override + * public MyAccum createAccumulator() { + * MyAccum accum = new MyAccum(); + * accum.list = new ListView<>(Types.STRING); + * accum.count = 0L; + * return accum; + * } + * + * //Overloaded accumulate method + * public void accumulate(MyAccum accumulator, String id) { + * accumulator.list.add(id); + * ... ... + * accumulator.get() + * ... ... + * } + * + * @Override + * public Long getValue(MyAccum accumulator) { + * accumulator.list.add(id); + * ... ... + * accumulator.get() + * ... ... + * return accumulator.count; + * } + * } + * + * }}} + * + * @param elementTypeInfo element type information + * @tparam T element type + */ +@TypeInfo(classOf[ListViewTypeInfoFactory[_]]) +class ListView[T](val elementTypeInfo: TypeInformation[T]) extends DataView { + + def this() = this(null) + + /** + * Returns an iterable of the list. + * + * @return The iterable of the list or { @code null} if the list is empty. + */ + def get: JIterable[T] = throw new UnsupportedOperationException("Unsupported operation!") --- End diff -- We try to implement public interfaces in a way that Java users do not need to deal with Scala classes. However, it should be fine in this case because 1. Scala's `UnsupportedOperationException` is defined as Java's `UnsupportedOperationException` 2. the exception will be removed if we implement the method by default as backed by an ArrayList. > 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. -- This message was sent by Atlassian JIRA (v6.4.14#64029)