Db migration

Skill justnau1020/claude-os/skills/development/db-migration

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Install

npx -y skills add justnau1020/claude-os --skill db-migration

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Guide through a database schema change. Use when you need to modify the database schema, add columns, create tables, or run migrations.

SKILL.md

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Database Migration

Guide a database schema change: $ARGUMENTS

Steps

1. Modify the model

Update the relevant model in the project's model/schema directory. ORM classes (SQLModel, SQLAlchemy, Prisma, etc.) define both the application model and the database schema.

2. Create migration

Generate the migration using the project's migration tool:

# Alembic (Python/SQLAlchemy)
alembic revision --autogenerate -m "$ARGUMENTS"

# Prisma (TypeScript/Node)
npx prisma migrate dev --name "$ARGUMENTS"

# Django
python manage.py makemigrations

Review the generated migration before applying.

3. Database-specific limitations

SQLite has limited ALTER TABLE support:

Can ADD COLUMN
Cannot DROP COLUMN (before SQLite 3.35)
Cannot ALTER COLUMN type
For complex changes, may need to recreate the table

PostgreSQL/MySQL support most ALTER TABLE operations but watch for:

Lock contention on large tables
Default values requiring table rewrites

If the migration requires unsupported operations, create a manual migration that:

Creates a new table with the desired schema
Copies data from the old table
Drops the old table
Renames the new table

4. Backup first

Before running any migration on production data:

# SQLite
cp database.db database.db.backup

# PostgreSQL
pg_dump dbname > backup.sql

5. Apply migration

# Alembic
alembic upgrade head

# Prisma
npx prisma migrate deploy

# Django
python manage.py migrate

6. Test

Write tests to verify:

New schema works with existing data
Migration is reversible (if supported by the migration tool)
Application still functions correctly with the new schema