database-migrations

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npx skills add langchain-ai/skills-benchmarks --skill database-migrations

Documentation

SKILL.md

npx skills add ...

Documentation

SKILL.md

Database Migration Patterns

Manage database schema changes safely and reliably.

Migration File Structure

migrations/
  001_create_users.sql
  002_add_email_index.sql
  003_create_orders.sql

Writing Safe Migrations

Adding Columns

-- migrations/004_add_user_status.sql
-- Up
ALTER TABLE users ADD COLUMN status VARCHAR(20) DEFAULT 'active';
CREATE INDEX idx_users_status ON users(status);
 
-- Down
DROP INDEX idx_users_status;
ALTER TABLE users DROP COLUMN status;

Creating Tables

-- migrations/005_create_audit_log.sql
-- Up
CREATE TABLE audit_log (
    id SERIAL PRIMARY KEY,
    table_name VARCHAR(100) NOT NULL,
    record_id INTEGER NOT NULL,
    action VARCHAR(20) NOT NULL,
    changed_by INTEGER REFERENCES users(id),
    changed_at TIMESTAMP DEFAULT NOW(),
    old_values JSONB,
    new_values JSONB
);
 
CREATE INDEX idx_audit_log_table ON audit_log(table_name, record_id);
CREATE INDEX idx_audit_log_time ON audit_log(changed_at);
 
-- Down
DROP TABLE audit_log;

Best Practices

Always include rollback (down) migrations
Never modify existing migrations - create new ones
Test migrations on a copy of production data
Use transactions for atomic changes
Add indexes concurrently in production: CREATE INDEX CONCURRENTLY