data-migration-builder

name	data-migration-builder
description	Use when writing data migrations (backfills, counter updates) with Alembic

Data Migration Builder

Pattern

def upgrade():
    op.execute("""
        UPDATE skills SET install_count = (
            SELECT COUNT(*) FROM installs
            WHERE installs.skill_id = skills.id AND installs.uninstalled_at IS NULL
        )
    """)

def downgrade():
    pass  # Data migrations typically not reversible

Backfill Strategy

For large tables, batch:

op.execute("UPDATE skills SET field = value WHERE id IN (SELECT id FROM skills LIMIT 1000)")

References

• Migrations: libs/db/alembic/versions/
• Alembic config: libs/db/alembic.ini