Mailing-List: contact commits-help@beam.incubator.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@beam.incubator.apache.org
Date: Fri, 4 Nov 2016 18:05:58 +0000 (UTC)
From: "Kenneth Knowles (JIRA)" <jira@apache.org>
To: commits@beam.incubator.apache.org
Message-ID: <JIRA.13018147.1478273746000.192989.1478282758951@Atlassian.JIRA>
In-Reply-To: <JIRA.13018147.1478273746000@Atlassian.JIRA>
References: <JIRA.13018147.1478273746000@Atlassian.JIRA> <JIRA.13018147.1478273746607@arcas>
Subject: =?utf-8?Q?[jira]_[Commented]_(BEAM-912)_?=
 =?utf-8?Q?Trigger_=08=08can_be_more_flexible?=
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
archived-at: Fri, 04 Nov 2016 18:06:53 -0000


    [ https://issues.apache.org/jira/browse/BEAM-912?page=3Dcom.atlassian.j=
ira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=3D156371=
98#comment-15637198 ]=20

Kenneth Knowles commented on BEAM-912:
--------------------------------------

Hello!

Your example does not actually seem to include triggers at all. Can you exp=
lain?

As for the suggestion itself: we have deliberately removed the {{onElement}=
} method and the rest of the state machine from Beam's triggers and made th=
em "just syntax". There are a few reasons for this:

 - User-defined triggers are not cross-language, yet. We need to design a l=
anguage-independent way for runners to invoke user-defined triggers.
 - Runners may actually have better ways of executing some triggers, so we =
don't want them to necessarily be black boxes.
 - There are many {{onElement}}-based state machines that are not correct t=
riggers. Even the triggers we have today took a while to get right - they a=
re not usable enough yet. So when we do create a cross-language cross-runne=
r user-defined trigger API, it won't look like the current API, but will be=
 more like the details I've added to BEAM-101. Basically a combiner and a p=
redicate.


> Trigger =08=08can be more flexible
> ------------------------------
>
>                 Key: BEAM-912
>                 URL: https://issues.apache.org/jira/browse/BEAM-912
>             Project: Beam
>          Issue Type: New Feature
>          Components: beam-model
>            Reporter: Jingsong Lee
>            Assignee: Frances Perry
>
> 1.We can support some data-driven trigger, so we need expose data in OnEl=
ementContext of onElement method.=20
> 2.We can support more flexible join, so we need expose buffer tag in Trig=
gerContext, now this buffer tag is in SystemReduceFn.
> for example: SELECT STREAM * FROM Orders AS o JOIN Shipments AS s
> ON o.orderId =3D s.orderId AND s.rowtime BETWEEN o.rowtime AND o.rowtime =
+ INTERVAL '1' HOUR;
> link: https://issues.apache.org/jira/browse/BEAM-101


--
This message was sent by Atlassian JIRA
(v6.3.4#6332)