alembicで外部キーを追加するときはCONSTRAINT 名を明示した方がいい

普通に alembic revision --autogenerate -m "add_os_version_id" でマイグレーションスクリプトを自動生成すると、 op.create_foreign_key op.drop_constraint の第一引数(CONSTRAINT名)が None となってしまう。

このスクリプトは alembic downgrade base 時に削除すべきCONSTERAINT名がわからずエラーになってしまう。

"""add_os_version_id

Revision ID: 6479768cd289
Revises: ecd9896cb55a
Create Date: 2024-01-25 11:40:11.027316

"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import mysql

# revision identifiers, used by Alembic.
revision = '6479768cd289'
down_revision = 'ecd9896cb55a'
branch_labels = None
depends_on = None


def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###

    op.add_column('devices', sa.Column('os_version_id', sa.Integer(), nullable=True))
    op.create_foreign_key(None, 'devices', 'os_versions', ['os_version_id'], ['id'], ondelete='RESTRICT')
    # ### end Alembic commands ###


def downgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.drop_constraint(None, 'devices', type_='foreignkey')
    op.drop_column('devices', 'os_version_id')
    # ### end Alembic commands ###

op.create_foreign_key op.drop_constraint の第一引数(CONSTRAINT名)に何らかの値を定義してあげると、alembic downgrade base でエラーにならなくなる。

"""add_os_version_id

Revision ID: 6479768cd289
Revises: ecd9896cb55a
Create Date: 2024-01-25 11:40:11.027316

"""
from alembic import op
import sqlalchemy as sa
from sqlalchemy.dialects import mysql

# revision identifiers, used by Alembic.
revision = '6479768cd289'
down_revision = 'ecd9896cb55a'
branch_labels = None
depends_on = None


def upgrade():
    # ### commands auto generated by Alembic - please adjust! ###

    op.add_column('devices', sa.Column('os_version_id', sa.Integer(), nullable=True))
    op.create_foreign_key("fk_devices_os_versions_id", 'devices', 'os_versions', ['os_version_id'], ['id'], ondelete='RESTRICT')
    # ### end Alembic commands ###


def downgrade():
    # ### commands auto generated by Alembic - please adjust! ###
    op.drop_constraint("fk_devices_os_versions_id", 'devices', type_='foreignkey')
    op.drop_column('devices', 'os_version_id')
    # ### end Alembic commands ###