Ignoring a model when using alembic autogenerate

问题

I am trying to autogenerate revisions for my DB using alembic. While doing so, I want to ignore some models (they have data types that are not supported by current version of MySQL). Here is what I tried and it seems to work fine, but I am not sure that's the most idiomatic way of doing it

inside alembic/env.py

def include_object(object, type_, name, reflected, compare_to):
    if type_ == 'table' and name == 'model_to_be_ignored':
        return False
    return True

and then inside run_migrations_online and run_migrations_offline I gave include_object=include_object and this seems to be working fine.

Ideally I would like to use skip_autogenerate=True, but not sure I can define that, so that later on I can simply remove that line in the models.py and get my desired behavior when I upgrade to newer version of database.

Is there something I am missing?

回答1:

As far as I can see, skip_autogenerate is not automatically handled by Alembic nor SQLAlchemy. But you can add it to Table.info like this:

Define a mixin that adds skip_autogenerate to Table.info. This is based in Flask-SQLAlchemy's BindMetaMixin

class ModelInfoMetaMixin(object):
    def __init__(cls, name, bases, d):
        skip_autogenerate = d.pop("__skip_autogenerate__", None)

        super(ModelInfoMetaMixin, cls).__init__(name, bases, d)

        if skip_autogenerate is not None and getattr(cls, "__table__", None) is not None:
            cls.__table__.info["skip_autogenerate"] = skip_autogenerate

Use this mixin to define a meta class and pass it to declarative_base()

from sqlalchemy.ext.declarative import DeclarativeMeta, declarative_base

class DefaultMeta(ModelInfoMetaMixin, DeclarativeMeta):
    pass

Model = declarative_base(cls=BaseModel, metaclass=DefaultMeta)

Then you can define your models with this marker:

class OneModel(Model):
    __skip_autogenerate__ = True
    uuid = Column(UUID(as_uuid=True), primary_key=True)

Finally, skip_autogenerate will be available in Alembic's include_object:

def include_object(object, name, type_, reflected, compare_to):
    # skip objects marked with "skip_autogenerate"
    if object.info.get("skip_autogenerate", False):
        return False

    return True

来源：https://stackoverflow.com/questions/54978681/ignoring-a-model-when-using-alembic-autogenerate

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python

sqlalchemy

alembic