= Using Alembic for schema migrations =

There are a few new requirements in requirements/dev.txt!  Be sure to get those installed.

Then, make a change to:

    socorro/external/postgresql/models.py

And then:

    PYTHONPATH=. alembic revision --autogenerate -m "Making an important change to the schema"

A migration script will be put into:

    alembic/versions

Now you can modify it to meet your needs. 

Then, to apply the migration:

    PYTHONPATH=. alembic upgrade head

Downgrade to previous revision:

    PYTHONPATH=. alembic downgrade -1


== Dealing with unsupported or custom TYPEs ==

We use a few types not currently supported by SQLAlchemy, so you may need to modify the migration slightly.

=== JSON example

Modify to import JSON type from socorro's model:

    from socorro.external.postgresql.models import JSON
    sa.Column(u'raw_crash', JSON(), nullable=False),

== Adding an index

    sa.Column(u'uuid', postgresql.UUID(), nullable=False, index=True, unique=True),