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https://issues.apache.org/jira/browse/FLINK-6233?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16096273#comment-16096273
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Xingcan Cui commented on FLINK-6233:
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[~fhueske], according to your comment, we actually not change the timestamp 
field, but consolidate them to be aligned with an existing watermark, which may 
be postponed by the operator, right?

> 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 < 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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