There are a few possibilities. You could have separate configuration files
for each database (eg. alembic-dev.ini and alembic-prod.ini), and choose
between them with the "--config" command line option.
If you want to stick to a single configuration file, you could put both
connection strings in your config file with different prefixes. For example:
sqlalchemy.dev.url = driver://user:pass@localhost/dbname
sqlalchemy.prod.url = driver://user:pass@localhost/dbname
Then, in your env.py file, locate the lines that say:
connectable = engine_from_config(
config.get_section(config.config_ini_section),
prefix="sqlalchemy.",
poolclass=pool.NullPool,
)
...and change it to use either "sqlalchemy.dev." or "sqlalchemy.prod." as
the prefix based on some condition. For example, you could use
"context.get_x_argument" and pass the environment name on the command line:
https://alembic.sqlalchemy.org/en/latest/api/runtime.html#alembic.runtime.environment.EnvironmentContext.get_x_argument
Hope that helps,
Simon
On Mon, May 9, 2022 at 8:57 PM thavha tsiwana <thavha.tsiw...@gmail.com>
wrote:
> wondering if there is more clearer information or a code snippet for this,
> I am also struggling to use 2 databases (1 dev, 1 prod) in my alembic
> project, I have successfully ran the migrations on the dev database, now I
> want to run my migrations to the prod database, I have no idea on how to
> modify alembic.ini and env.py file,,, please help
>
> On Tuesday, 01 February 2022 at 15:08:20 UTC+2 skira....@gmail.com wrote:
>
>> 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
>>>
>> --
> SQLAlchemy -
> The Python SQL Toolkit and Object Relational Mapper
>
> http://www.sqlalchemy.org/
>
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--
SQLAlchemy -
The Python SQL Toolkit and Object Relational Mapper
http://www.sqlalchemy.org/
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