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From "Stu Hood (JIRA)" <>
Subject [jira] Commented: (CASSANDRA-1311) Support (asynchronous) triggers
Date Wed, 23 Feb 2011 08:12:38 GMT


Stu Hood commented on CASSANDRA-1311:

I believe that the entity group functionality can actually be implemented as sugar on top
of our existing secondary indexes and column nesting (I'll describe what I'm thinking of on
that ticket).

This ticket, on the other hand, provides novel functionality, so my vote is strongly in favor
of getting it in mostly-as-is, with slight adjustments:
* ITriggers should be configured to match a filter, as described on CASSANDRA-1601. Rather
than triggering for any change to a row, it should trigger for changes to a set of names,
or a slice of names. For example: setting a trigger for columns 'age' and 'state' would only
fire the trigger if either of those columns changed
* The ITrigger contract should not guarantee to give the user all changed columns: only the
columns matching the trigger configuration.

I'm hoping that in future tickets we can unify these ''at-least-once'' distributed triggers
with our ''exactly-once'' local indexes (with UDFs) around common configuration: see CASSANDRA-1601.

> Support (asynchronous) triggers
> -------------------------------
>                 Key: CASSANDRA-1311
>                 URL:
>             Project: Cassandra
>          Issue Type: New Feature
>          Components: Contrib
>            Reporter: Maxim Grinev
>             Fix For: 0.8
>         Attachments: HOWTO-PatchAndRunTriggerExample-update1.txt, HOWTO-PatchAndRunTriggerExample.txt,
ImplementationDetails-update1.pdf, ImplementationDetails.pdf, trunk-967053.txt, trunk-984391-update1.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:
> An example of using triggers for indexing:
> Implementation details are attached.

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