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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-6233) Support rowtime inner equi-join between two streams in the SQL API
Date Tue, 19 Sep 2017 08:51:01 GMT

    [ https://issues.apache.org/jira/browse/FLINK-6233?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16171333#comment-16171333
] 

ASF GitHub Bot commented on FLINK-6233:
---------------------------------------

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

    https://github.com/apache/flink/pull/4625#discussion_r139631978
  
    --- Diff: flink-libraries/flink-table/src/main/scala/org/apache/flink/table/runtime/join/RowTimeBoundedStreamInnerJoin.scala
---
    @@ -0,0 +1,83 @@
    +/*
    + * 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.runtime.join
    +
    +import org.apache.flink.api.common.typeinfo.TypeInformation
    +import org.apache.flink.streaming.api.functions.co.CoProcessFunction
    +import org.apache.flink.table.runtime.types.CRow
    +import org.apache.flink.types.Row
    +
    +/**
    +  * The function to execute row(event) time bounded stream inner-join.
    +  */
    +class RowTimeBoundedStreamInnerJoin(
    +    leftLowerBound: Long,
    +    leftUpperBound: Long,
    +    allowedLateness: Long,
    +    leftType: TypeInformation[Row],
    +    rightType: TypeInformation[Row],
    +    genJoinFuncName: String,
    +    genJoinFuncCode: String,
    +    leftTimeIdx: Int,
    +    rightTimeIdx: Int)
    +    extends TimeBoundedStreamInnerJoin(
    +      leftLowerBound,
    +      leftUpperBound,
    +      allowedLateness,
    +      leftType,
    +      rightType,
    +      genJoinFuncName,
    +      genJoinFuncCode,
    +      leftTimeIdx,
    +      rightTimeIdx,
    +      JoinTimeIndicator.ROWTIME) {
    +
    +  override def checkRowOutOfDate(timeForRow: Long, watermark: Long) = {
    +    timeForRow <= watermark - allowedLateness
    +  }
    +
    +  override def updateOperatorTime(ctx: CoProcessFunction[CRow, CRow, CRow]#Context):
Unit = {
    +    rightOperatorTime =
    +      if (ctx.timerService().currentWatermark() > 0) ctx.timerService().currentWatermark()
    --- End diff --
    
    After checking the codes, I find out that the number of watermark usages is even larger
than that of their updates (i.e., each update is followed by at least one usage). Considering
that the number of usage may increase in the future, I suggest to keep this check in the update
method. Of course, it would be better if we can use a "safer" initial value for
     the watermarkšŸ˜„. What do you think? 


> Support rowtime inner equi-join between two streams in the SQL API
> ------------------------------------------------------------------
>
>                 Key: FLINK-6233
>                 URL: https://issues.apache.org/jira/browse/FLINK-6233
>             Project: Flink
>          Issue Type: Sub-task
>          Components: Table API & SQL
>            Reporter: hongyuhong
>            Assignee: Xingcan Cui
>
> The goal of this issue is to add support for inner equi-join on proc time streams to
the SQL interface.
> Queries similar to the following should be supported:
> {code}
> SELECT o.rowtime , o.productId, o.orderId, s.rowtime AS shipTime 
> FROM Orders AS o 
> JOIN Shipments AS s 
> ON o.orderId = s.orderId 
> AND o.rowtime BETWEEN s.rowtime AND s.rowtime + INTERVAL '1' HOUR;
> {code}
> The following restrictions should initially apply:
> * The join hint only support inner join
> * The ON clause should include equi-join condition
> * The time-condition {{o.rowtime BETWEEN s.rowtime AND s.rowtime + INTERVAL '1' HOUR}}
only can use rowtime that is a system attribute, the time condition only support bounded time
range like {{o.rowtime BETWEEN s.rowtime - INTERVAL '1' HOUR AND s.rowtime + INTERVAL '1'
HOUR}}, not support unbounded like {{o.rowtime &lt; s.rowtime}} ,  and  should include
both two stream's rowtime attribute, {{o.rowtime between rowtime () and rowtime () + 1}} should
also not be supported.
> An row-time streams join will not be able to handle late data, because this would mean
in insert a row into a sorted order shift all other computations. This would be too expensive
to maintain. Therefore, we will throw an error if a user tries to use an row-time stream join
with late data handling.
> This issue includes:
> * Design of the DataStream operator to deal with stream join
> * Translation from Calcite's RelNode representation (LogicalJoin). 



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