Homepage

How to Remove Old Database Migrations in Ruby on Rails

Rails data migration should be performed in accordance with some rules, tips and notes, so that you won’t need ages to finish it. This is all the more important when you are tasked with creating a clear development environment setup, and removing old records is key. Check how we did that when we overtook one of the Ruby projects.

Recently we’ve overtaken a big project for maintenance and further development. It’s a Rails application with many models, controllers and of course lots of database migrations. There were about one hundred files in db/migrate directory. The question is: how can we setup development environment with current database structure? Running rake db:migrate would just be a suicide. It won’t simply work, because these migrations were written long time ago and the current code and models implementation don’t fit them. Instead let’s load schema.rb file using this command:

tsx

It will create all needed tables for models and also a special table schema_migrations to track migrations. Selecting all rows you will see something like this:

tsx

So, how can we use this special table to get rid of smelly migration files?

The solution

We can just create new migration and copy all add/create statements from schema.rb

tsx

The migration can look like this:

tsx

Then we need to change it a little bit, because we don’t won’t to lose any data while deploying new migration to staging or/and production environment. Just remove force: true option to make sure we will never lose any data by recreating tables. So let’s try to run this new migration:

tsx

Yes, well, it didn’t work, because we’ve already loaded schema.rb and all our tables are already there. So what can we do? We can use the latest version of migration from our schema_migrations and rename the new one:

tsx

Finally, we can remove all migrations excluding the current one:

tsx

Now, if we run db:migrate we won’t see any results or errors because we’ve have already migrated the database. However, if we have to setup a new environment we can run all (one) our migrations without any problems.

What’s left?

There is a small problem with this solution. If you have migrations which are modifying data like adding admin account or so, you need to find them manually and copy the code to our structure migration or add a new migration. The data is not included in schema.rb

Ending…

We just removed all migrations by adding new one with the whole structure. We can now continue hacking and adding new migrations in normal way. Above steps can be repeated any time we want. So, you can keep small number of migrations. Just be careful when you have new migrations on your local branch, but they are not deployed to staging or production yet. It won’t work. You need too rollback your local migrations until it matches staging/production and then copy schema.rb

Thanks all for now. Thank you and bye :)

Let’s Create a Great Website Together

We'll shape your web platform the way you win it!

More posts in this category

  • February 05, 2025 • 10 min read

    API-first CMS: What Options You Have (Web Dev Agency's Take)

    According to the 2024 State of the API Report by Postman, 74% of organizations are adopting API-first strategies. This statistic isn’t just impressive—it signals a major shift in how businesses operate. While API-first approaches have long been a staple in software development, they're now reshaping content management as well. More and more companies are realizing that traditional CMS platforms can't keep up with the demand for flexibility, speed, and seamless integrations.

    READ MORELearn more about api first cms
  • January 23, 2025 • 15 min read

    Best CMS for SaaS: Top Cloud-Based Solutions

    Choosing the right Content Management System (CMS) is a critical decision for your SaaS business. Your unique needs require solutions that are not only flexible, scalable, and user-friendly but also tailored to meet the demands of a fast-paced, customer-focused industry. A CMS should simplify your workflows and help you deliver personalized, high-quality digital experiences.

    READ MORELearn more about best cms for saas top cloud based solutions
  • December 12, 2024 • 10 min read

    We Picked the Best (Headless) CMS for Vue

    Picture a digital experience where content effortlessly flows across platforms, development is agile, and performance is unmatched. By combining the power of Vue.js, a progressive JavaScript framework, with a modern headless CMS, you can achieve all this and more.

    READ MORELearn more about headless cms for vue