RescueUniqueConstraint

ActiveRecord doesn’t do a great job of rescuing ActiveRecord::RecordNotUnique
violations resulting from a duplicate entry on a database level unique constraint.

This gem automatically rescues the error and instead adds a validation error
on the field in question, making it behave as if you had a normal uniqueness
validation.

Note that if you have only a unique constraint in the database and no uniqueness validation in ActiveRecord, it
is possible for your object to validate but then fail to save.

See Usage for more info.

Installation

Add this line to your application’s Gemfile:

gem 'rescue_unique_constraint'

And then execute:

$ bundle

Or install it yourself as:

$ gem install rescue_unique_constraint

Usage

Assuming you’ve added unique index:

class AddIndexToThing < ActiveRecord::Migration
  disable_ddl_transaction!

  def change
    add_index :things, :somefield, unique: true, algorithm: :concurrently, name: "my_unique_index"
  end
end

Before:

class Thing < ActiveRecord::Base
end

thing = Thing.create(somefield: "foo")
dupe = Thing.create(somefield: "foo")
# => raises ActiveRecord::RecordNotUnique

Note that if you have validates :uniqueness in your model, it will prevent
the RecordNotUnique from being raised in some cases, but not all, as race
conditions between multiple processes will still cause duplicate entries to
enter your database.

After:

class Thing < ActiveRecord::Base
  include RescueUniqueConstraint
  rescue_unique_constraint index: "my_unique_index", field: "somefield"
end

thing = Thing.create(somefield: "foo")
dupe = Thing.create(somefield: "foo")
# => false
thing.errors[:somefield] == "somefield has already been taken"
# => true
# => raises ActiveRecord::RecordNotUnique

Testing

You’ll need a database that supports unique constraints.
This gem has been tested with PostgreSQL, MySQL and SQLite.

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request