Reference article:
https://docs.openstack.org/mitaka/networking-guide/migration-database.html
https://docs.openstack.org/neutron/pike/contributor/alembic_migrations.html#expand-and-contract-scripts
The database upgrade of the neutron service is implemented through the Alembic tool, and the neutron-db-manage command is a wrapper for alembic.
neutron-db-manage --help View command usage information
neutron-db-manage