Open Stack

On 5/14/15 11:40 AM, Mike Bayer wrote:
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> Assuming I can get that done in the next few months, the next step 
> would be that the migration streams can be broken into branches, e.g. 
> juno, kilo, liberty, etc. so that we can easily add new migration 
> files that are backportable in place to a target backport.   
> Additionally, the issue of end-user migrations that are divergent from 
> what is part of Nova itself should also be achieved using additional 
> branches; if a customer wants to make their own changes to a database, 
> such as adding extra indexes, this can be done in their own 
> user-specific branch that will integrate with the primary migration 
> stream.    That would eliminate the need for a system that is tasked 
> with diffing live database schemas and then executing decisions 
> directly without any chance to review or version-control the changes 
> that are being made.

I would also note that this system can maintain the "expand" and 
"contract" idea from the online schema changes system, such that the 
migration files themselves would be organized into branches for "expand" 
and "contract" that can be run separately (the current Alembic branching 
model did not exist at the time that the online schema changes spec was 
written).   This way the ability to run just the "expansion" in one 
phase and the "contract" in another can be maintained; it's just the 
migration steps themselves would live in version-controlled migration 
files as they always do.

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>> Does that help?
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>> Thanks,
>> John
>>
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