contributing-docs/13_metadata_database_updates.rst

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Metadata Database Updates
=========================

When developing features, you may need to persist information to the metadata
database. Airflow has `Alembic <https://github.com/sqlalchemy/alembic>`__ built-in
module to handle all schema changes. Alembic must be installed on your
development machine before continuing with migration.


.. code-block:: bash

    # starting at the root of the project
    $ pwd
    ~/airflow
    # change to the airflow directory
    $ cd airflow
    $ alembic revision -m "add new field to db"
       Generating
    ~/airflow/airflow/migrations/versions/a1e23c41f123_add_new_field_to_db.py

Note that migration file names are standardized by pre-commit hook ``update-migration-references``, so that they sort alphabetically and indicate
the Airflow version in which they first appear (the alembic revision ID is removed). As a result you should expect to see a pre-commit failure
on the first attempt.  Just stage the modified file and commit again
(or run the hook manually before committing).

After your new migration file is run through pre-commit it will look like this:

.. code-block::

    1234_A_B_C_add_new_field_to_db.py

This represents that your migration is the 1234th migration and expected for release in Airflow version A.B.C.

--------

You can also learn how to setup your `Node environment <14_node_environment_setup.rst>`__ if you want to develop Airflow UI.