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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pavel Yaskevich updated CASSANDRA-1391:
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Attachment: CASSANDRA-1391.patch
Update{Keyspace/ColumnFamily) migrations now update only modified fields
instead of blindly copying everything, applyModels can be skipped now if it
makes no modifications.
Merge algorithm is based on isolated schema initialized from merging migration
lastVersion point: merging migration applied first then all older migrations,
after that Schema.instance gets safely updated.
Rebased with latest trunk (last commit 38a55bab7ee054bce83028b5f0abda3e9e9e7ebf)
> Allow Concurrent Schema Migrations
> ----------------------------------
>
> Key: CASSANDRA-1391
> URL: https://issues.apache.org/jira/browse/CASSANDRA-1391
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Stu Hood
> Assignee: Pavel Yaskevich
> Fix For: 1.0
>
> Attachments:
> 0001-CASSANDRA-1391-refactoring-of-the-DatabaseDescriptor.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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