What did you use Alembic for?

I used Alembic for managing database migrations in SQLAlchemy applications.

Main tasks solved by Alembic:

• Creating and modifying tables: Automatic generation of scripts based on changes in SQLAlchemy models.
• Updating the database schema: Step-by-step application or rollback of migrations to change data structure.
• Migration history: Tracking applied and available migrations, which facilitates synchronization between teams and environments.
• Separation of business logic and schema changes: SQL commands for ALTER TABLE are in separate files, simplifying code maintenance.

Example of using a command to generate a migration

# Generate the first migration
alembic revision -m "create_users_table"

# Automatic generation of migration based on model changes
alembic revision --autogenerate -m "add_email_to_users"

Example of a migration file

"""add_email_to_users

Revision ID: 123456789abc
Revises: abcdef123456
Create Date: 2023-10-27 10:00:00.000000

"""
from alembic import op
import sqlalchemy as sa


# revision identifiers, used by Alembic.
revision = '123456789abc'
down_revision = 'abcdef123456'
branch_labels = None
depends_on = None


def upgrade():
    # Adding 'email' column to 'users' table
    op.add_column('users', sa.Column('email', sa.String(), nullable=True))


def downgrade():
    # Removing 'email' column
    op.drop_column('users', 'email')

Commands for applying and rolling back migrations:

# Apply all pending migrations
alembic upgrade head

# Roll back the last migration
alembic downgrade -1

Using Alembic greatly simplifies the process of project development requiring database structure changes and reduces the risk of errors during deployment.