PR: Move to Alembic for database migrations (v3)

[Thomas De Schampheleire]

On Mon, Jul 18, 2016 at 7:26 PM, Søren Løvborg <sorenl at unity3d.com> wrote:
> I've posted a new version of my Alembic work here:
>
> https://kallithea-scm.org/repos/kallithea/pull-request/52
>
> I'm still working on a migration to clean up the old cruft that have
> accumulated in Kallithea databases over the years; this is
> unfortunately a quite complex task, what with three database engines
> to support, and an altogether unruly database model. :-)
>
> But if this code is accepted, we could begin to take simpler changes
> to the database, like added columns and such.
>
>
> From the PR description
> -----------------------
>
> This PR:
> - corrects a few quirks in our current database model, as a
> prerequisite for the following work
> - removes remaining RhodeCode compatibility
> - removes SQLAlchemy Migrate database migration library
> - adds basic Alembic database migration support
> - adds well-defined key/index/constraint naming (for new databases only...)
> - documents how to use Alembic
>
> It also (in the last two commits) demonstrates the use of Alembic for
> a semi-complex database migration; these two commits are not actually
> intended to be merged. Feel free to comment on the Alembic usage, but
> don't waste your time on the actual demo feature, which is unfinished
> and will be PR'ed separately when/if it is ready. :-)
>
> Unlike the previous iterations, this PR has actually been tested on
> MySQL and PostgreSQL, uncovering a number of surprising little
> problems (fixed, among other places, in the first three commits).
>
> Remaining work:
> - Use Alembic to clean up old cruft in the database.
>
> Please review the individual changesets, and feel free to comment here
> on the mailing list.
>
> For reviewing the documentation changes, I've also put a doc build up here:
> https://files.unity3d.com/sorenl/f468d970f906/
>
> In particular, you may want to read the new "Upgrading Kallithea":
> https://files.unity3d.com/sorenl/f468d970f906/upgrade.html
>
> And the new "Database schema changes":
> https://files.unity3d.com/sorenl/f468d970f906/dev/dbmigrations.html
>

I reviewed and gave my comments on the PR directly...