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On Fri, May 15, 2015 at 11:54 AM, Mike Bayer <mbayer at redhat.com> wrote:

>
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> On 5/14/15 7:12 PM, Angus Salkeld wrote:
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> On Fri, May 15, 2015 at 4:46 AM, Mike Bayer <mbayer at redhat.com> wrote:
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>>
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>> On 5/14/15 11:58 AM, Doug Hellmann wrote:
>>
>>>
>>> At one point we were exploring having both sqlalchemy-migrate and
>>> alembic run, one after the other, so that we only need to create new
>>> migrations with alembic and do not need to change any of the existing
>>> migrations. Was that idea dropped?
>>>
>>
>>  to my knowledge the idea wasn't dropped.   If a project wants to
>> implement that using the oslo.db system, that is fine, however from my POV
>> I'd prefer to just port the SQLA-migrate files over and drop the migrate
>> dependency altogether.  Whether or not a project does the "run both" step
>> as an interim step doesn't affect that effort very much.
>>
>>
>  Hi Mike
>
>  Just a quick question: How would the alembic scripts know where to start
> the migration from if the current installation had been up until that
> point been using migrate (I believe both alembic and migrate write to a
> small table what the current version is, would you look for that?)?
>
> Thinking about that issue, the most controllable and clean-break way to do
> it would be to add support to Alembic itself that augments its own handling
> of the "alembic_version" table to transfer data from an existing
> sqlalchemy_migrate table.  I can even see using traditional alembic
> hex-style version numbers in migration files which then also can refer to
> their previous numerically-based migrate file.
>
> It's not unreasonable that Alembic would support some standard upgrade
> path from Migrate, the only other migration tool SQLAlchemy has ever had,
> so I'd just add that as a feature.
>

Thanks. Would you suggest we hold off moving to alembic (in Heat) until you
have this ironed out? I just want to make sure we
don't do this prematurely.

-Angus


>
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>  -Angus
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>
>>
>>
>>
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