If you have git example, share, please.
On Monday, 30 April 2012 at 04:10:14 UTC+3 limodou wrote:
> On Sun, Apr 29, 2012 at 11:13 PM, Michael Bayer
> <mik...@zzzcomputing.com> wrote:
> >
> > On Apr 29, 2012, at 10:56 AM, limodou wrote:
> >
> >> On Sun, Apr 29, 2012 at 10:42 PM, Michael Bayer
> >> <mik...@zzzcomputing.com> wrote:
> >>> You would assemble a multi-database scheme of your choosing in env.py.
> If you do "alembic init multidb" you'll see an example of one. How
> env.py is organized depends greatly on the relationship of the databases to
> each other, that is, to what degree they are mirrors of each other versus
> storing different schemas.
> >>>
> >>
> >> If I ran the command:
> >>
> >> alembic init multidb
> >>
> >> It'll create multidb folder and copy files in it. But I saw the
> >> alembic.ini will be the same one. So if I should change it myself? And
> >> how to let alembic know different database when executing commands
> >> like: revision, upgrade, etc. It seems that no database parameter
> >> existed.
> >>
> >> And if I can manage different databases in one directory or in one ini
> file?
> >
> > multidb has a different alembic.ini as an example. If you already had
> an alembic.ini there it wouldn't overwrite it.
> >
> > if you really wanted two completely independent sets of migration
> scripts, then you'd run two migration environments.
> >
> > They can share the same alembic.ini like this:
> >
> > [my_db_one]
> > sqlalchemy.url =
> >
> > [my_db_two]
> > sqlalchemy.url =
> >
> > you then run alembic with "alembic -n my_db_one" or "alembic -n
> my_db_two". The "default" config area is set by -n.
> >
> > A single env.py script can get multiple database URLs in any way it
> wants, as it determines how config is accessed. If you look in the
> multidb/env.py script, you'll see it's pulling multiple database urls from
> one section using config.get_section(name) - config file:
> >
> > [alembic]
> > # path to migration scripts
> > script_location = ${script_location}
> >
> > # template used to generate migration files
> > # file_template = %%(rev)s_%%(slug)s
> >
> > databases = engine1, engine2
> >
> > [engine1]
> > sqlalchemy.url = driver://user:pass@localhost/dbname
> >
> > [engine2]
> > sqlalchemy.url = driver://user:pass@localhost/dbname2
> >
> > usage:
> >
> > config = context.config
> >
> > db_names = config.get_main_option('databases')
> >
> > for name in re.split(r',\s*', db_names):
> > engines[name] = rec = {}
> > rec['engine'] = engine_from_config(
> > config.get_section(name),
> > prefix='sqlalchemy.',
> > poolclass=pool.NullPool)
> >
> > Over here I have both forms of multi db at the same time. There's two
> migration environments, and one migration environment does two databases
> that are largely mirrored, so three databases total. All three make use
> of a common env.py script that's in my application as a library, they then
> implement an env.py in the migration environment that draws upon the
> myapp/lib/env.py script for common features.
> >
> > You can pass instructions to a single env.py that may be controlling
> multiple databases using --tag:
> >
> > "alembic --tag my_tag"
> >
> > "my_tag" is available in env.py as context.get_tag_argument(). You can
> use that to conditionally run migrations on one database or the other.
> >
> > This is all DIY. Multi-database migrations can happen in many different
> ways so you'd need to build the approach that suits your situation best.
> >
> >
>
> thank you very much.
>
>
> --
> I like python!
> UliPad <<The Python Editor>>: http://code.google.com/p/ulipad/
> UliWeb <<simple web framework>>: http://code.google.com/p/uliweb/
> My Blog: http://hi.baidu.com/limodou
>
--
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The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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