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Flask-Migrate is an extension that handles SQLAlchemy database migrations for Flask applications using Alembic. Alembic is a lightweight database migration tool for usage with SQLAlchemy. It allows developers to manage database schema changes over time in a consistent and easy manner.
When working with Flask-Migrate, you might encounter an error indicating an Alembic version mismatch. This typically manifests as an error message during migration operations, such as:
alembic.util.exc.CommandError: Can't locate revision identified by 'some_revision_id'
This error suggests that the Alembic version in your database does not match the migration scripts in your project.
The root cause of this issue is often due to discrepancies between the migration scripts and the database's current state. This can happen if migrations were not applied correctly, or if the database was altered outside of the migration scripts.
For more details on Alembic, you can refer to the official Alembic documentation.
Ensure that your migration scripts are up-to-date. Check the migrations/versions
directory in your project for the latest migration files.
Run the following command to check the current version of your database:
flask db current
This will show the current revision ID in the database.
If there are pending migrations, apply them using:
flask db upgrade
This command will apply all pending migrations to bring the database schema up-to-date.
If the issue persists, you might need to manually adjust the database version. Use the following command to stamp the database with the correct version:
flask db stamp head
This will set the database's version to the latest migration script without applying any changes.
By following these steps, you should be able to resolve the Alembic version mismatch issue in your Flask application. Always ensure that your migration scripts are in sync with your database to prevent such issues. For further reading, you can explore the Flask-Migrate documentation.
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