alembic-offline 2.0.0
Offline extensions for Alembic database migration framework for SQLAlchemy
Requires Python: >=3.8

alembic-offline
===============

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alembic-offline is an extension for Alembic to enrich offline functionality of migrations using SQLAlchemy

.. contents::

Usage
-----

Phased migrations
^^^^^^^^^^^^^^^^^

alembic-offline introduces a helper which allows to implement phased migrations, e.g. those which steps
are divided into logical phases. For example, you can have steps to be executed before code deploy and
those after.

In your alembic config file (main section):

::

    phases = before-deploy after-deploy final
    default-phase = after-deploy

In your version file:

.. code-block:: python

    from sqlalchemy import INTEGER, VARCHAR, NVARCHAR, TIMESTAMP, Column, func
    from alembic import op

    from alembic_offline import phased, execute_script

    from tests.migrations.scripts import script

    revision = '1'
    down_revision = None


    @phased
    def upgrade():

        op.create_table(
            'account',
            Column('id', INTEGER, primary_key=True),
            Column('name', VARCHAR(50), nullable=False),
            Column('description', NVARCHAR(200)),
            Column('timestamp', TIMESTAMP, server_default=func.now())
        )
        yield
        op.execute("update account set name='some'")
        yield
        execute_script(script.__file__)


    def downgrade():
        pass

Will give the sql output (for sqlite):

.. code-block:: sql

    -- Running upgrade  -> 1

    -- PHASE::before-deploy::;

    CREATE TABLE account (
        id INTEGER NOT NULL,
        name VARCHAR(50) NOT NULL,
        description NVARCHAR(200),
        timestamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
        PRIMARY KEY (id)
    );

    -- PHASE::after-deploy::;

    update account set name='some';

    -- PHASE::final::;

    -- SCRIPT::scripts/script.py::;

    INSERT INTO alembic_version (version_num) VALUES ('1');

As you see, phases are rendered as SQL comments to divide migration steps, so those who execute migration
can see which phase's step it is.
However, if migration procedure is highly customized, you can use alembic-offline API described below.
`get_migration_data` returns migration phases in special form so you can automate their execution.

Arbitrary script as operation
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

For complex migrations, it's not enough to execute sql, you might need some script to be executed instead.
For that, there's special operation:

.. code-block:: python

    from alembic_offline import execute_script

    def upgrade():
        execute_script('scripts/script.py')

If you'll get migration sql, it will be rendered as SQL comment:

.. code-block:: sql

    -- SCRIPT::scripts/script.py::;

For those who execute migrations it will be visible and they can execute the script manually.
However, if migration procedure is highly customized, you can use alembic-offline API described below.
`get_migration_data` returns script migration steps in special form so you can automate their execution.
For online mode, the script will be executed as subprocess via python `subprocess` module.

Get migration data
^^^^^^^^^^^^^^^^^^

alembic-offline provides specialized API to get certain migration data as dictionary:

.. code-block:: python

    from alembic_offline import get_migration_data

    from alembic.config import Config

    config = Config('path to alembic.ini')

    data = get_migration_data(config, 'your-revision')

    assert data == {
        'revision': 'your-revision',
        'phases': {
            'after-deploy': [
                {
                    'type': 'mysql',
                    'script': 'alter table account add column name VARCHAR(255)'
                },
                {
                    'type': 'python',
                    'script': 'from app.models import Session, Account; Session.add(Account()); Session.commit()',
                    'path': 'scripts/my_script.py'
                },
            ]
        }
    }

`get_migration_data` requires both `phases` and `default-phase` configuration options to be set.
`default-phase` is needed to be able to get migration data even for simple migrations without phases.

Get migration data in batch
^^^^^^^^^^^^^^^^^^^^^^^^^^^

alembic-offline provides an API call to get migration data for all revisions:

.. code-block:: python

    from alembic_offline import get_migrations_data

    from alembic.config import Config

    config = Config('path to alembic.ini')

    data = get_migrations_data(config)

    assert data == [
        {
            'revision': 'your-revision',
            'phases': {
                'after-deploy': [
                    {
                        'type': 'mysql',
                        'script': 'alter table account add column name VARCHAR(255)'
                    },
                    {
                        'type': 'python',
                        'script': 'from app.models import Session, Account; Session.add(Account()); Session.commit()',
                        'path': 'scripts/my_script.py'
                    },
                ]
            }
        }
    ]

Contact
-------

If you have questions, bug reports, suggestions, etc. please create an issue on
the `GitHub project page <http://github.com/paylogic/alembic-offline>`_.

License
-------

This software is licensed under the `MIT license <http://en.wikipedia.org/wiki/MIT_License>`_

© 2015 Anatoly Bubenkov, Paylogic International and others.