---
name: data-migration-scripts
description: >
  Create safe, reversible database migration scripts with rollback capabilities,
  data validation, and zero-downtime deployments. Use when changing database
  schemas, migrating data between systems, or performing large-scale data
  transformations.
---

# Data Migration Scripts

## Table of Contents

- [Overview](#overview)
- [When to Use](#when-to-use)
- [Quick Start](#quick-start)
- [Reference Guides](#reference-guides)
- [Best Practices](#best-practices)

## Overview

Create robust, safe, and reversible data migration scripts for database schema changes and data transformations with minimal downtime.

## When to Use

- Database schema changes
- Adding/removing/modifying columns
- Migrating between database systems
- Data transformations and cleanup
- Splitting or merging tables
- Changing data types
- Adding indexes and constraints
- Backfilling data
- Multi-tenant data migrations

## Quick Start

Minimal working example:

```typescript
import { Knex } from "knex";

// migrations/20240101000000_add_user_preferences.ts
export async function up(knex: Knex): Promise<void> {
  // Create new table
  await knex.schema.createTable("user_preferences", (table) => {
    table.uuid("id").primary().defaultTo(knex.raw("gen_random_uuid()"));
    table
      .uuid("user_id")
      .notNullable()
      .references("id")
      .inTable("users")
      .onDelete("CASCADE");
    table.jsonb("preferences").defaultTo("{}");
    table.timestamp("created_at").defaultTo(knex.fn.now());
    table.timestamp("updated_at").defaultTo(knex.fn.now());

    table.index("user_id");
  });

  // Migrate existing data
  await knex.raw(`
    INSERT INTO user_preferences (user_id, preferences)
    SELECT id, jsonb_build_object(
      'theme', COALESCE(theme, 'light'),
// ... (see reference guides for full implementation)
```

## Reference Guides

Detailed implementations in the `references/` directory:

| Guide | Contents |
|---|---|
| [Knex.js Migrations (Node.js)](references/knexjs-migrations-nodejs.md) | Knex.js Migrations (Node.js) |
| [Alembic Migrations (Python/SQLAlchemy)](references/alembic-migrations-pythonsqlalchemy.md) | Alembic Migrations (Python/SQLAlchemy) |
| [Large Data Migration with Batching](references/large-data-migration-with-batching.md) | Large Data Migration with Batching |
| [Zero-Downtime Migration Pattern](references/zero-downtime-migration-pattern.md) | Zero-Downtime Migration Pattern |
| [Migration Validation](references/migration-validation.md) | Migration Validation |
| [Cross-Database Migration](references/cross-database-migration.md) | Cross-Database Migration |

## Best Practices

### ✅ DO

- Always write both `up` and `down` migrations
- Test migrations on production-like data
- Use transactions for atomic operations
- Process large datasets in batches
- Add indexes after data insertion
- Validate data after migration
- Log progress and errors
- Use feature flags for application code changes
- Back up database before running migrations
- Test rollback procedures
- Document migration side effects
- Version control all migrations
- Use idempotent operations

### ❌ DON'T

- Run untested migrations on production
- Make breaking changes without backwards compatibility
- Process millions of rows in single transaction
- Skip rollback implementation
- Ignore migration failures
- Modify old migrations
- Delete data without backups
- Run migrations manually in production


---
Source attribution: aj-geddes
Original project: https://github.com/aj-geddes/useful-ai-prompts/blob/3f5182cfd739fc113f4af5244a1cf342ad7f7911/skills/data-migration-scripts/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2025 AJ Geddes

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.


# Mega AI Hub resource metadata

Creator / publisher: aj-geddes
Original project: https://github.com/aj-geddes/useful-ai-prompts/blob/3f5182cfd739fc113f4af5244a1cf342ad7f7911/skills/data-migration-scripts/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering
Roles: Backend Developer, Data Engineer, Database Administrator
Specialties: Database
Tools: Tool not specified
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 6ee2bf4efb248fbeab4eb0e5d9d651e71f80439abfa3210ebfe743a7c4ff1787