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https://issues.apache.org/jira/browse/JAMES-3578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17340043#comment-17340043
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Raphael Ouazana commented on JAMES-3578:
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Could we at least have a documentation page explaining clearly what is the
upgrade path for each version?
> 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
>
>
> 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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