Write unique validation with confidence!

It’s easy to use model validation in Rails application and in this article, we will study some aspects with the uniqueness validator.

So let’s start with an easy requirement, we want to have an Account model with a unique email attribute.

This solution works but it’s not enough. For beginners, it’s important to understand how validation work in Rails. So from Rails guide, we can check the following:

Creating and saving a new record will send an SQL INSERT operation to the database. Updating an existing record will send an SQL UPDATE operation instead. Validations are typically run before these commands are sent to the database.

As we can see from the quote, if we submit two duplicate models at the same time it’s possible to bypass this validation. To test this scenario we will use Parallel gem, just add the following line to your Gemfile and don’t forget to run bundle install

For testing purpose we will add this method in Account class:

And now from Rails console:

what a surprise! We have duplicate records now. To fix this issue we just need to add a unique database index for email column.


That’s it, with this simple approach we have a less issue to worry about 🙂