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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13181379#comment-13181379
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Sylvain Lebresne commented on CASSANDRA-1391:
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bq. Let me get this clear - migrations use apply/diff internally for their
actions upon KEYSPACE_CF
But then why do the patches still use thrift internally (I have only quickly
eyeballed the patches but it does seem to use thrift, which seems confirmed by
Jonathan comments).
bq. sending MIGRATION_REQUEST message with list of its local migrations attached
Does that mean we still keep the list of all migrations (diffs) that have ever
been applied? If so, I would be in favor of getting rid of it, as it seems to
me we can do without (node could use the diffs between their schema and another
node schema and base whatever action have to be done (directories creation,
etc...) on that, be we wouldn't keep the diff afterwards).
bq. Current schema distribution is switched to be pull oriented
This is probably not a huge deal but it means that schema changes will be a tad
slower, based on gossip reactivity.
> 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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