[GitHub] flink pull request #4355: [FLINK-7206] [table] Implementation of DataView to...

[kaibozhou <gi...@git.apache.org>]

Github user kaibozhou commented on a diff in the pull request:

    https://github.com/apache/flink/pull/4355#discussion_r130606340
  
    --- 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[_]])
    --- End diff --
    
    I tried and it will compile with error "not found: type T"


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