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https://issues.apache.org/jira/browse/CASSANDRA-8928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15183144#comment-15183144
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Paulo Motta commented on CASSANDRA-8928:
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[~kdmu] Nice start! You're in the right direction but I suggest focusing on
downgrading from "ma" (3.x) to "la" (2.2) format first, since the new native
storage format introduced on 3.0 is what will probably take the most of your
time to understand and get right. In order to familiarize yourself with the 3.0
storage format (which is brand new) I suggest you read [this blog
post|http://thelastpickle.com/blog/2016/03/04/introductiont-to-the-apache-cassandra-3-storage-engine.html].
For a more practical task you can you can do a similar breakdown of the 2.2
format (if you can't find any available), what will make visualize better the
main changes needed between these formats.
Also, another important goal of this ticket is to provide a generic framework
that will allow to downgrade sstables in future versions, so we should design
it in a way that it can be reused to downgrade between different formats,
rather than hard-coding to specific conversions. So before diving into hardcore
implementation I suggest you to write a brief design document describing an
overview of the downgrade process and its main interfaces and/or modules, so we
can make sure we're on the same page before you start.
> Add downgradesstables
> ---------------------
>
> Key: CASSANDRA-8928
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8928
> Project: Cassandra
> Issue Type: New Feature
> Components: Tools
> Reporter: Jeremy Hanna
> Priority: Minor
> Labels: gsoc2016, mentor
>
> As mentioned in other places such as CASSANDRA-8047 and in the wild,
> sometimes you need to go back. A downgrade sstables utility would be nice
> for a lot of reasons and I don't know that supporting going back to the
> previous major version format would be too much code since we already support
> reading the previous version.
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