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From "Nate McCall (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1311) Triggers
Date Thu, 08 Nov 2012 01:34:16 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13492883#comment-13492883
] 

Nate McCall commented on CASSANDRA-1311:
----------------------------------------

That brings up a point - what about DROP TRIGGER semantics? I'd call that 'minimum essential'
as well. 

bq. We should bring up the trigger class in a separate class loader (or some other method)
so they can be reloaded.

Appealing, but two non-trivial issues with dynamic classloading, IME:
- leaks that keep the classloader from getting collected and end up with an OOM in PermGen
that takes down the whole JVM (number of 'public static final' refs in cassandra code base
could/will be linked to will exacerbate this)
- coordinating such in a cluster == hard (tomcat folks never really got it right)

You could get all OSGi, but that's a mess unto itself. 

Otherwise, super glad to see this issue resurrected :)
                
> Triggers
> --------
>
>                 Key: CASSANDRA-1311
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1311
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Maxim Grinev
>            Assignee: Vijay
>             Fix For: 1.3
>
>         Attachments: HOWTO-PatchAndRunTriggerExample.txt, HOWTO-PatchAndRunTriggerExample-update1.txt,
ImplementationDetails.pdf, ImplementationDetails-update1.pdf, trunk-967053.txt, trunk-984391-update1.txt,
trunk-984391-update2.txt
>
>
> Asynchronous triggers is a basic mechanism to implement various use cases of asynchronous
execution of application code at database side. For example to support indexes and materialized
views, online analytics, push-based data propagation.
> Please find the motivation, triggers description and list of applications:
> http://maxgrinev.com/2010/07/23/extending-cassandra-with-asynchronous-triggers/
> An example of using triggers for indexing:
> http://maxgrinev.com/2010/07/23/managing-indexes-in-cassandra-using-async-triggers/
> Implementation details are attached.

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