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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-8158) Rowtime window inner join emits late data
Date Wed, 29 Nov 2017 03:51:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-8158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16270090#comment-16270090
] 

ASF GitHub Bot commented on FLINK-8158:
---------------------------------------

Github user hequn8128 commented on the issue:

    https://github.com/apache/flink/pull/5094
  
    Hi @xccui , thanks for your reply. Feel free to take it if you wish. I still have some
confusions. 
    1. Considering the test `testRowTimeJoinWithCommonBounds2` in `JoinHarnessTest`, do you
mean the row with timestamp 1000 should not been calculated? The row does satisfy the join
condition: `t1.rt BETWEEN t2.rt - INTERVAL '5' SECOND AND t2.rt + INTERVAL '1' SECOND`, and
this is the difference between `BETWEEN` and `NOT BETWEEN`.
    2. Can't we use the holding back watermark as the boundary to cache and expire data? Any
data with timestamp bigger than the holding back watermark should be cached and may be joined
later.  We should take any opportunity to join and produce a result that satisfy the join
predicate.


> Rowtime window inner join emits late data
> -----------------------------------------
>
>                 Key: FLINK-8158
>                 URL: https://issues.apache.org/jira/browse/FLINK-8158
>             Project: Flink
>          Issue Type: Bug
>          Components: Table API & SQL
>            Reporter: Hequn Cheng
>            Assignee: Hequn Cheng
>         Attachments: screenshot-1xxx.png
>
>
> When executing the join, the join operator needs to make sure that no late data is emitted.
Currently, this achieved by holding back watermarks. However, the window border is not handled
correctly. For the sql bellow: 
> {quote}
>     val sqlQuery =
>       """
>         SELECT t2.key, t2.id, t1.id
>         FROM T1 as t1 join T2 as t2 ON
>           t1.key = t2.key AND
>           t1.rt BETWEEN t2.rt - INTERVAL '5' SECOND AND
>             t2.rt + INTERVAL '1' SECOND
>         """.stripMargin
>     val data1 = new mutable.MutableList[(String, String, Long)]
>     // for boundary test
>     data1.+=(("A", "LEFT1", 6000L))
>     val data2 = new mutable.MutableList[(String, String, Long)]
>     data2.+=(("A", "RIGHT1", 6000L))
> {quote}
> Join will output a watermark with timestamp 1000, but if left comes with another data
("A", "LEFT1", 1000L), join will output a record with timestamp 1000 which equals previous
watermark.



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