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From "Stu Hood (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1311) Support (asynchronous) triggers
Date Fri, 13 Aug 2010 19:26:30 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1311?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12898378#action_12898378
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Stu Hood commented on CASSANDRA-1311:
-------------------------------------

An interesting benefit provided by CASSANDRA-1016 is that it has a pre-execution step, allowing
the Plugin/Trigger to perform a read if it needs to (for example, to update a compound index
which the mutation does not contain all columns for).

Since making the read-then-write step atomic is out of the question, the benefit is questionable
(something I think we missed when we were considering 1016). Requiring the user to use mutations
containing all fields the trigger might need may be reasonable. Example: for updating the
zipcode in an index of "country-zipcode", it would be up to the user to include both fields
in the mutation, meaning that they might have to perform a read from their base data first.

> Support (asynchronous) triggers
> -------------------------------
>
>                 Key: CASSANDRA-1311
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1311
>             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:
> 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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