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From "Pavel Yaskevich (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-1391) Allow Concurrent Schema Migrations
Date Fri, 06 Jan 2012 21:10:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13181606#comment-13181606
] 

Pavel Yaskevich commented on CASSANDRA-1391:
--------------------------------------------

It doesn't feel to simple for me to do it in one big run - where you would need to go through
whole schema (possibly few times) comparing to applying a single well-defined change. We are
not expecting migrations to be very frequent e.g. because special conditions should be ensured
according to ks/cf getting updated, so even with 1000 (I don't know if it's even a real deal)
migrations it's not a problem for a new node to get them in one request and apply sequentially.
 
                
> 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-new-migration-distribution-schema.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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