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https://issues.apache.org/jira/browse/JAMES-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benoit Tellier closed JAMES-3578.
---------------------------------
    Resolution: Fixed

https://github.com/apache/james-project/pull/417 contributed this.

> Post 3.6.x Cassandra data schema sanitizing
> -------------------------------------------
>
>                 Key: JAMES-3578
>                 URL: https://issues.apache.org/jira/browse/JAMES-3578
>             Project: James Server
>          Issue Type: Improvement
>          Components: cassandra, mailbox, RRT
>            Reporter: Benoit Tellier
>            Priority: Major
>             Fix For: 3.7.0
>
>          Time Spent: 2.5h
>  Remaining Estimate: 0h
>
> For multiple reasons, our Cassandra schemas evolve over time and we end up 
> adapting the tables structure over time.
> To migrate data from the old to the new table organisation, the Apache James 
> project:
>  - Support backward compatibility and will lookup the old tables if needed, 
> sometime performing on the fly data migration.
>  - Provide migration tasks for moving the data from the old tables to the new.
> Of course all this logic is complex and needs to be maintained:
>  - More tests needs to be ran as we need to ensure correctness regardless of 
> the schema version
>  - More bugs resulting from interaction between this migration logic and 
> other features like read-repairs
>  - More code meaning heavier maintenance costs
>  - More Cassandra tables being created, which have a detrimental impact on 
> performance (marginal yes but still... 
> https://thelastpickle.com/blog/2020/11/25/impacts-of-many-tables-on-cassandra.html
>  )
> Here are the migration we currently support:
> {code:java}
> allMigrationClazzBinder.addBinding(FROM_V5_TO_V6).to(MailboxPathV2Migration.class);
>         
> allMigrationClazzBinder.addBinding(FROM_V6_TO_V7).to(MappingsSourcesMigration.class);
>         
> allMigrationClazzBinder.addBinding(FROM_V7_TO_V8).to(MailboxPathV3Migration.class);
>         
> allMigrationClazzBinder.addBinding(FROM_V8_TO_V9).to(MessageV3Migration.class);
>         
> allMigrationClazzBinder.addBinding(FROM_V9_TO_V10).to(AclV2Migration.class);
> {code}
> I propose to drop MailboxPathV2Migration, MappingsSourcesMigration, 
> MailboxPathV3Migration.
> Doing so allows dropping 2 tables and remove 3.000 lines of code. Users will 
> need to upgrade from 3.6.x to perform these migrations before moving on to 
> 3.7.x...



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