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https://issues.apache.org/jira/browse/CASSANDRA-4684?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13467866#comment-13467866
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Sylvain Lebresne commented on CASSANDRA-4684:
---------------------------------------------
The use case is for client that want to maintain a view of the schema up to
date. After all, with CQL3 we're going into a more typed world, so it make
sense that high level client would need to know about those types. For
instance, you cannot form a query properly unless you know the schema. And in
1.2, creating tables dynamically will be a fully supported use case, so in that
case you will likely need to access the current schema programatically. But
even without that, I'm pretty sure that any advanced tooling like say a good
eclipse plugin will need to keep an up to date view of the schema.
Without this patch, said client will have to either query the schema each and
every time they need it, or implement some form of ad-hoc polling. But events
are here exactly to avoid having to do polling (and clients will already have
support for events, so it will much easier for them to have this).
> Binary protocol: inform clients of schema changes
> -------------------------------------------------
>
> Key: CASSANDRA-4684
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4684
> Project: Cassandra
> Issue Type: Improvement
> Affects Versions: 1.2.0 beta 1
> Reporter: Sylvain Lebresne
> Assignee: Sylvain Lebresne
> Priority: Minor
> Fix For: 1.2.0 beta 2
>
> Attachments: 0001-Return-schema-change-infos.txt,
> 0002-Add-migration-events.txt
>
>
> It would be nice to inform clients when a schema change occurs as this would
> allow said client to maintain the current state of the schema, which might be
> useful/desirable. To allow that, we can:
> # return that a query has changed the schema (instead of simply a 'void'
> return), in the same spirit than CASSANDRA-3707.
> # add events notification on schema change.
> Just to be clear, the goal is only to inform that a change has occured, the
> client would still have to query the system table to know the exact content
> of the change, but at least it'll know when to do such query.
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