database-migration

★ 37,559

by wshobson · part of wshobson/agents

Execute database migrations across ORMs and platforms with zero-downtime strategies, data transformation, and rollback procedures. Use when migrating databases, changing schemas, performing data transformations, or implementing zero-downtime deployment strategies.

🧩 One of 7 skills in the wshobson/agents package — works on its own, and pairs well with its siblings.

This is the playbook your agent receives when the skill activates — you don't need to read it to use the skill, but it's here to audit before installing.

Database Migration

Master database schema and data migrations across ORMs (Sequelize, TypeORM, Prisma), including rollback strategies and zero-downtime deployments.

When to Use This Skill

Migrating between different ORMs
Performing schema transformations
Moving data between databases
Implementing rollback procedures
Zero-downtime deployments
Database version upgrades
Data model refactoring

ORM Migrations

Sequelize Migrations

// migrations/20231201-create-users.js
module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.createTable("users", {
      id: {
        type: Sequelize.INTEGER,
        primaryKey: true,
        autoIncrement: true,
      },
      email: {
        type: Sequelize.STRING,
        unique: true,
        allowNull: false,
      },
      createdAt: Sequelize.DATE,
      updatedAt: Sequelize.DATE,
    });
  },

  down: async (queryInterface, Sequelize) => {
    await queryInterface.dropTable("users");
  },
};

// Run: npx sequelize-cli db:migrate
// Rollback: npx sequelize-cli db:migrate:undo

TypeORM Migrations

// migrations/1701234567-CreateUsers.ts
import { MigrationInterface, QueryRunner, Table } from "typeorm";

export class CreateUsers1701234567 implements MigrationInterface {
  public async up(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.createTable(
      new Table({
        name: "users",
        columns: [
          {
            name: "id",
            type: "int",
            isPrimary: true,
            isGenerated: true,
            generationStrategy: "increment",
          },
          {
            name: "email",
            type: "varchar",
            isUnique: true,
          },
          {
            name: "created_at",
            type: "timestamp",
            default: "CURRENT_TIMESTAMP",
          },
        ],
      }),
    );
  }

  public async down(queryRunner: QueryRunner): Promise<void> {
    await queryRunner.dropTable("users");
  }
}

// Run: npm run typeorm migration:run
// Rollback: npm run typeorm migration:revert

Prisma Migrations

// schema.prisma
model User {
  id        Int      @id @default(autoincrement())
  email     String   @unique
  createdAt DateTime @default(now())
}

// Generate migration: npx prisma migrate dev --name create_users
// Apply: npx prisma migrate deploy

Schema Transformations

Adding Columns with Defaults

// Safe migration: add column with default
module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.addColumn("users", "status", {
      type: Sequelize.STRING,
      defaultValue: "active",
      allowNull: false,
    });
  },

  down: async (queryInterface) => {
    await queryInterface.removeColumn("users", "status");
  },
};

Renaming Columns (Zero Downtime)

// Step 1: Add new column
module.exports = {
  up: async (queryInterface, Sequelize) => {
    await queryInterface.addColumn("users", "full_name", {
      type: Sequelize.STRING,
    });

    // Copy data from old column
    await queryInterface.sequelize.query("UPDATE users SET full_name = name");
  },

  down: async (queryInterface) => {
    await queryInterface.removeColumn("users", "full_name");
  },
};

// Step 2: Update application to use new column

// Step 3: Remove old column
module.exports = {
  up: async (queryInterface) => {
    await queryInterface.removeColumn("users", "name");
  },

  down: async (queryInterface, Sequelize) => {
    await queryInterface.addColumn("users", "name", {
      type: Sequelize.STRING,
    });
  },
};

Changing Column Types

module.exports = {
  up: async (queryInterface, Sequelize) => {
    // For large tables, use multi-step approach

    // 1. Add new column
    await queryInterface.addColumn("users", "age_new", {
      type: Sequelize.INTEGER,
    });

    // 2. Copy and transform data
    await queryInterface.sequelize.query(`
      UPDATE users
      SET age_new = CAST(age AS INTEGER)
      WHERE age IS NOT NULL
    `);

    // 3. Drop old column
    await queryInterface.removeColumn("users", "age");

    // 4. Rename new column
    await queryInterface.renameColumn("users", "age_new", "age");
  },

  down: async (queryInterface, Sequelize) => {
    await queryInterface.changeColumn("users", "age", {
      type: Sequelize.STRING,
    });
  },
};

Data Transformations

Complex Data Migration

module.exports = {
  up: async (queryInterface, Sequelize) => {
    // Get all records
    const [users] = await queryInterface.sequelize.query(
      "SELECT id, address_string FROM users",
    );

    // Transform each record
    for (const user of users) {
      const addressParts = user.address_string.split(",");

      await queryInterface.sequelize.query(
        `UPDATE users
         SET street = :street,
             city = :city,
             state = :state
         WHERE id = :id`,
        {
          replacements: {
            id: user.id,
            street: addressParts[0]?.trim(),
            city: addressParts[1]?.trim(),
            state: addressParts[2]?.trim(),
          },
        },
      );
    }

    // Drop old column
    await queryInterface.removeColumn("users", "address_string");
  },

  down: async (queryInterface, Sequelize) => {
    // Reconstruct original column
    await queryInterface.addColumn("users", "address_string", {
      type: Sequelize.STRING,
    });

    await queryInterface.sequelize.query(`
      UPDATE users
      SET address_string = CONCAT(street, ', ', city, ', ', state)
    `);

    await queryInterface.removeColumn("users", "street");
    await queryInterface.removeColumn("users", "city");
    await queryInterface.removeColumn("users", "state");
  },
};

Rollback Strategies

Transaction-Based Migrations

module.exports = {
  up: async (queryInterface, Sequelize) => {
    const transaction = await queryInterface.sequelize.transaction();

    try {
      await queryInterface.addColumn(
        "users",
        "verified",
        { type: Sequelize.BOOLEAN, defaultValue: false },
        { transaction },
      );

      await queryInterface.sequelize.query(
        "UPDATE users SET verified = true WHERE email_verified_at IS NOT NULL",
        { transaction },
      );

      await transaction.commit();
    } catch (error) {
      await transaction.rollback();
      throw error;
    }
  },

  down: async (queryInterface) => {
    await queryInterface.removeColumn("users", "verified");
  },
};

Checkpoint-Based Rollback

module.exports = {
  up: async (queryInterface, Sequelize) => {
    // Create backup table
    await queryInterface.sequelize.query(
      "CREATE TABLE users_backup AS SELECT * FROM users",
    );

    try {
      // Perform migration
      await queryInterface.addColumn("users", "new_field", {
        type: Sequelize.STRING,
      });

      // Verify migration
      const [result] = await queryInterface.sequelize.query(
        "SELECT COUNT(*) as count FROM users WHERE new_field IS NULL",
      );

      if (result[0].count > 0) {
        throw new Error("Migration verification failed");
      }

      // Drop backup
      await queryInterface.dropTable("users_backup");
    } catch (error) {
      // Restore from backup
      await queryInterface.sequelize.query("DROP TABLE users");
      await queryInterface.sequelize.query(
        "CREATE TABLE users AS SELECT * FROM users_backup",
      );
      await queryInterface.dropTable("users_backup");
      throw error;
    }
  },
};

Additional patterns and templates

More detailed templates and worked examples live in references/details.md. Read that file for the full pattern library.