Github user sunjincheng121 commented on a diff in the pull request:

    https://github.com/apache/flink/pull/3386#discussion_r102927451
  
    --- Diff: 
flink-libraries/flink-table/src/main/scala/org/apache/flink/table/plan/nodes/datastream/DataStreamSlideEventTimeRowAgg.scala
 ---
    @@ -0,0 +1,179 @@
    +/*
    + * 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.plan.nodes.datastream
    +
    +import org.apache.calcite.plan.{RelOptCluster, RelTraitSet}
    +import org.apache.calcite.rel.`type`.RelDataType
    +import org.apache.calcite.rel.core.AggregateCall
    +import org.apache.calcite.rel.{RelNode, RelWriter, SingleRel}
    +import org.apache.flink.api.java.tuple.Tuple
    +import org.apache.flink.types.Row
    +import org.apache.flink.table.calcite.{FlinkRelBuilder, FlinkTypeFactory}
    +import FlinkRelBuilder.NamedWindowProperty
    +import org.apache.flink.table.runtime.aggregate.AggregateUtil._
    +import org.apache.flink.table.runtime.aggregate._
    +import org.apache.flink.streaming.api.datastream.{AllWindowedStream, 
DataStream, WindowedStream}
    +import org.apache.flink.streaming.api.windowing.assigners._
    +import org.apache.flink.streaming.api.windowing.windows.{Window => 
DataStreamWindow}
    +import org.apache.flink.table.api.StreamTableEnvironment
    +import org.apache.flink.table.plan.nodes.CommonAggregate
    +
    +class DataStreamSlideEventTimeRowAgg(
    +    namedProperties: Seq[NamedWindowProperty],
    +    cluster: RelOptCluster,
    +    traitSet: RelTraitSet,
    +    inputNode: RelNode,
    +    namedAggregates: Seq[CalcitePair[AggregateCall, String]],
    +    rowRelDataType: RelDataType,
    +    inputType: RelDataType,
    +    grouping: Array[Int])
    +  extends SingleRel(cluster, traitSet, inputNode)
    +  with CommonAggregate
    +  with DataStreamRel {
    +
    +  override def deriveRowType(): RelDataType = rowRelDataType
    +
    +  override def copy(traitSet: RelTraitSet, inputs: 
java.util.List[RelNode]): RelNode = {
    +    new DataStreamSlideEventTimeRowAgg(
    +      namedProperties,
    +      cluster,
    +      traitSet,
    +      inputs.get(0),
    +      namedAggregates,
    +      getRowType,
    +      inputType,
    +      grouping)
    --- End diff --
    
    I think `I check whether the current data is out of order in WindowOperator 
isLate function, and now just discard if islate.`  will not work well. Because  
the logic in this method is:
    ```
    if (windowAssigner instanceof GlobalEventTimeRowWindowAssigner) {
                                return 
windowAssignerContext.getCurrentElementTime() < 
windowAssignerContext.getCurrentMaxTime();
                        } 
    ```
    e.g. Test Data:
    ```
    1, 1L, "Hi", 1400000L
    2, 2L, "Hello", 1400005L
    3, 2L, "Hello w", 1300000
    4, 3L, "Hello world", 1400010L
    ```
    You do not know which element first comes, so you will get different 
results every time you run it,Just like:
    `SELECT` d, SUM(a)  over (order by rowtime() range between unbounded 
preceding and current row) from T1`
    You can get the following results:
    The first time:
    ```
    1400005,2
    1400010,6
    ```
    The second time
    ```
    1400000,1
    1400010,5
    ```
    The third time
    ```
    1300000,3
    1400005,5
    1400010,9
    ```
    So,IMHO. Event-time over must handle the situation above. How do you 
think?


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