Agent Skills: Database Migrations

Database Migrations

Location: backend/db/migrations/

Create Migration

1. Create NNN_description.sql (next sequential number)
2. Write idempotent SQL
3. Run npm run db:migrate

Patterns

-- New table
CREATE TABLE IF NOT EXISTS user_preferences (
  id SERIAL PRIMARY KEY,
  user_id INTEGER NOT NULL,
  theme VARCHAR(50) DEFAULT 'light',
  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
);

-- Add column
ALTER TABLE ideas ADD COLUMN IF NOT EXISTS new_field TEXT;

-- JSONB column
ALTER TABLE ideas ADD COLUMN IF NOT EXISTS quick_notes JSONB;

-- Index
CREATE INDEX IF NOT EXISTS idx_ideas_domain ON ideas(domain);

-- pgvector
CREATE EXTENSION IF NOT EXISTS vector;
ALTER TABLE ideas ADD COLUMN IF NOT EXISTS embedding vector(1536);

After Migration

1. Update backend/src/types/index.ts - add interface properties
2. Update backend/src/repositories/*Repository.ts - update mapFromDb

Gotchas

• Always IF NOT EXISTS - idempotent migrations
• No rollback - fix failures manually
• Check state first - \d tablename in psql
• JSONB for flexible data - evolving structures