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Gary Dusbabek commented on CASSANDRA-2056:
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bq. This is obsolete post-CASSANDRA-1391
This ticket is orthogonal to 1391. The purpose for flattening schemas is to
make is so we do not have to maintain compatibility for the migration
serializers indefinitely (for the purpose of bootstrapping a new node).
> Need a way of flattening schemas.
> ---------------------------------
>
> Key: CASSANDRA-2056
> URL: https://issues.apache.org/jira/browse/CASSANDRA-2056
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Gary Dusbabek
> Priority: Minor
> Attachments: v2-0001-convert-MigrationManager-into-a-singleton.txt,
> v2-0002-bail-on-migrations-originating-from-newer-protocol-ver.txt,
> v2-0003-a-way-to-upgrade-schema-when-protocol-version-changes.txt
>
>
> For all of our trying not to, we still managed to screw this up. Schema
> updates currently contain a serialized RowMutation stored as a column value.
> When a node needs updated schema, it requests these values, deserializes them
> and applies them. As the serialization scheme for RowMutation changes over
> time (this is inevitable), those old migrations will become incompatible with
> newer implementations of the RowMutation deserializer. This means that when
> new nodes come online, they'll get migration messages that they have trouble
> deserializing. (Remember, we've only made the promise that we'll be
> backwards compatible for one version--see CASSANDRA-1015--even though we'd
> eventually have this problem without that guarantee.)
> What I propose is a cluster command to flatten the schema prior to upgrading.
> This would basically purge the old schema updates and replace them with a
> single serialized migration (serialized in the current protocol version).
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