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https://issues.apache.org/jira/browse/CASSANDRA-1391?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13180604#comment-13180604
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Jonathan Ellis commented on CASSANDRA-1391:
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bq. 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?
At the least, it lets you re-use apply/diff instead of rewriting that, and easy
CASSANDRA-2477.
bq. 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
Does it? It sure looks like it uses serialized Thrift objects to me. (Looking
at DefsTable.loadFromStorage.)
> 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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