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From "Jingsong Lee (JIRA)" <>
Subject [jira] [Commented] (BEAM-912) Trigger can be more flexible
Date Tue, 08 Nov 2016 02:50:58 GMT


Jingsong Lee commented on BEAM-912:

Thanks for your advice, but there are some problems. For example, We want to a2 merge b1 and
a2 merge b2, but don't want to b1 merge b2 in the drawing. But  MergeContextImpl will throw
IllegalArgumentException if any elements of toBeMerged have already been merged. If we merge
b1 and b2, the output is too late to a2b1 that is we don't want to see.

> Trigger can be more flexible
> ------------------------------
>                 Key: BEAM-912
>                 URL:
>             Project: Beam
>          Issue Type: New Feature
>          Components: beam-model
>            Reporter: Jingsong Lee
>            Assignee: Kenneth Knowles
>         Attachments: betweenJoin.png
> 1.We can support some data-driven trigger, so we need expose data in OnElementContext
of onElement method. 
> 2.We can support more flexible join, so we need expose buffer tag in TriggerContext,
now this buffer tag is in SystemReduceFn.
> for example: SELECT STREAM * FROM Orders AS o JOIN Shipments AS s
> ON o.orderId = s.orderId AND s.rowtime BETWEEN o.rowtime AND o.rowtime + INTERVAL '1'
> link:

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