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From "Paulo Motta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-8928) Add downgradesstables
Date Mon, 07 Mar 2016 15:33:40 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-8928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15183144#comment-15183144
] 

Paulo Motta commented on CASSANDRA-8928:
----------------------------------------

[~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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