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From "Jonathan Ellis (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1391) Allow Concurrent Schema Migrations
Date Thu, 15 Dec 2011 16:18:31 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13170322#comment-13170322
] 

Jonathan Ellis commented on CASSANDRA-1391:
-------------------------------------------

That doesn't work, though: what if we have two updates at the same timestamp?  I think it
really does need to be content-based.

Also, I still think using Table.apply and CF.diff is the "right" way to do this, instead of
effectively duplicating that code as a special case.  Are there any downsides to that approach
I'm missing?
                
> 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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