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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13170908#comment-13170908
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Pavel Yaskevich commented on CASSANDRA-1391:
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Isn't that an over-complication? Starting from step 2 in your previous comment,
node would always need to do diff to all of the CF objects plus determine were
any of the keyspaces deleted/added which on the other hand migrations give us
for free because we always know exactly what does migration modify. Also when
node starts with such content-based version and it's version does not much
others, does it really know what to do - send own schema or request one?.. I
also think that once ring will get to some frequency of the schema changes it
would create a noticeable traffic and nodes won't be able to keep up migrating
anymore...
> Allow Concurrent Schema Migrations
> ----------------------------------
>
> Key: CASSANDRA-1391
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1391
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Affects Versions: 0.7.0
> Reporter: Stu Hood
> Assignee: Pavel Yaskevich
> Fix For: 1.1
>
> Attachments:
> 0001-new-migration-schema-and-avro-methods-cleanup.patch,
> 0002-avro-removal.patch, 0003-oldVersion-removed-nit-fixed.patch,
> CASSANDRA-1391.patch
>
>
> CASSANDRA-1292 fixed multiple migrations started from the same node to
> properly queue themselves, but it is still possible for migrations initiated
> on different nodes to conflict and leave the cluster in a bad state. Since
> the system_add/drop/rename methods are accessible directly from the client
> API, they should be completely safe for concurrent use.
> It should be possible to allow for most types of concurrent migrations by
> converting the UUID schema ID into a VersionVectorClock (as provided by
> CASSANDRA-580).
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