Benoit Tellier created JAMES-3578:
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Summary: 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
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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