How to run alembic check in a read-only database

[CarlHey]

I have a read-only database. I use alembic to check if my SQLAlchemy model definition matches the database table schema. Howerer, running alembic check requires creating alembic_version table in the database. Is there a way to use alembic while not creating version table?

[CaselIT]

Hi,

The check commands uses the autogenerate features, that in general will query the alembic_version table to setup the environment and check that all available migrations are applied in the db before performing a check.

What's your use care for wanting to use alembic but not having the alembic_version table in the db?

[CarlHey]

Thanks for your reply. I'm working on a tool for a series of services that share most of the same table structure, but with some differences. I defined the SQLAlchemy ORM models based on the table structure, and then used alembic to check that the models were consistent with the database schemas for those services. In my use case, only the orm models and database schemas need to be compared, and there is no need of versioning of the database migration, so even if there is a 'alembic_version' table, its current version would always be empty. I only have read-only access to these databases, so alembic fails when trying to create the version table. I want to know if there is a way to just compare the code to the database schema, or to have Alembic treat the current version of the database as empty, without actually create the version table.

[zzzeek]

Alembic's API can be used to run a metadata / reflection comparison , a complete example is at https://alembic.sqlalchemy.org/en/latest/api/autogenerate.html#alembic.autogenerate.compare_metadata

[CarlHey]

Thank you. That's exactly what I'm looking for.