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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180559#comment-13180559
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Pavel Yaskevich commented on CASSANDRA-1391:
--------------------------------------------
I still don't see how/why apply/diff would be better than migrations (which are
localized actions on the schema)...
bq. allow dropping the last_migration_key indirection
We can drop it even with my current patches but what does it give us? Instead
of converting deserialized thrift objects to KSMetaData we would need to
initialize KSMetaData/CFMetaData and populate those with parameters from db, is
it really better?
bq. pave the way for CASSANDRA-2477
With current patch user will be able to do "SELECT * FROM system.keyspaces" and
other queries but after CASSANDRA-2474 is done because `system.keyspaces` uses
composite columns.
> 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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