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From "Pavel Yaskevich (JIRA)" <>
Subject [jira] [Updated] (CASSANDRA-1391) Allow Concurrent Schema Migrations
Date Fri, 26 Aug 2011 16:40:29 GMT


Pavel Yaskevich updated CASSANDRA-1391:

    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:
>             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-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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