alembic-offline
===============
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alembic-offline is an extension for alemic to enrich offline functionality of the migrations
.. 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 alemic.config import Config
config = Config('path to alemic.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 alemic.config import Config
config = Config('path to alemic.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'
},
]
}
}
]
Command line utilities
^^^^^^^^^^^^^^^^^^^^^^
Because with alembic revisions it's sometimes hard to find which the correct down revision should be; especially
when there are multiple heads we added the alembic-offline graph command.
The graph command will generate a `dot file <https://en.wikipedia.org/wiki/DOT_(graph_description_language)>`_ of
the revisions, this file can then be converted to an image for easy visualization.
Usage:
::
alembic-offline graph --filename revisions.dot --alembic-config path/to/alembic.ini
Then if you have `graphviz <https://en.wikipedia.org/wiki/Graphviz>`_ installed you can run:
::
dot -Tpng -o revisions.png revisions.dot
To generate a png image.
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>`_
Please refer to the `license file <https://github.com/paylogic/alembic-offline/blob/master/LICENSE.txt>`_
© 2015 Anatoly Bubenkov, Paylogic International and others.
Changelog
=========
1.2.0
-----
* add migration dependency tree generation command (hvdklauw)
1.1.0
-----
* add down_revision to migration data (bubenkoff)
* reverse migration order to simplify the application (bubenkoff)
1.0.5
-----
* correctly handle multi-phased migration data extraction (bubenkoff)
1.0.4
-----
* online script execution implemented (bubenkoff)
* `get_migrations_data` API (bubenkoff)
1.0.3
-----
* Added arbitrary script operation (bubenkoff)
* Strict phases configuration assertions for phased migration decorator (bubenkoff)
* `get_migration_data` API (bubenkoff)
1.0.0
-----
* Initial public release (bubenkoff)