DatabaseValidations

DatabaseValidations helps you to keep the database consistency with better performance. Right now, it supports only ActiveRecord.

The more you use the gem, the more performance increase you have. Try it now!

Installation

Add this line to your application's Gemfile:

gem 'database_validations'

And then execute:

bundle

Or install it yourself as:

gem install database_validations

Have a look at example application for details.

Benchmark (code)

Imagine, you have User model defines as

class User < ActiveRecord::Base
  validates :email, :full_name, uniqueness: true

  belongs_to :company
  belongs_to :country
end

and then replace with

class User < ActiveRecord::Base
  validates :email, :full_name, db_uniqueness: true
  # OR
  # validates_db_uniqueness_of :email, :full_name

  db_belongs_to :company
  db_belongs_to :country
  # OR
  # belongs_to :company
  # belongs_to :country
  # validates :company, :country, db_presence: true
end

you will get the following performance improvement:

Caveats

• db_belongs_to doesn't work with SQLite due to a poor error message.
• In Rails 4, the gem validations work differently than the ActiveRecord ones when validate: false option is passed to save/save!. They incorrectly return a validation message instead of raising a proper constraint violation exception. In Rails >= 5 they correctly raise the exceptions they supposed to.

db_belongs_to

Supported databases are PostgreSQL and MySQL. Note: Unfortunately, SQLite raises a poor error message by which we can not determine exact foreign key which raised an error.

Usage

class User < ActiveRecord::Base
  db_belongs_to :company
end

user = User.create(company_id: nil)
# => false
user.errors.messages
# => {:company=>["must exist"]}

Problem

ActiveRecord's belongs_to has optional: false by default. Unfortunately, this approach does not ensure existence of the related object. For example, we can skip validations or remove the related object after we save the object. After that, our database becomes inconsistent because we assume the object has his relation but it does not.

db_belongs_to solves the problem using foreign key constraints in the database also providing backward compatibility with nice validations errors.

Pros and Cons

Advantages:

• Ensures relation existence because it uses foreign keys constraints.
• Checks the existence of proper foreign key constraint at the boot time. Use ENV['SKIP_DB_UNIQUENESS_VALIDATOR_INDEX_CHECK'] = 'true' if you want to skip it in some cases. (For example, when you run migrations.) Note: we skip it for the abstract classes.
• It's almost two times faster because it skips unnecessary SQL query. See benchmarks below for details.

Disadvantages:

• Cannot handle multiple database validations at once because database raises only one error per query.

Configuration options

Benchmarks (code)

validates_db_uniqueness_of

Supported databases are PostgreSQL, MySQL and SQLite.

Usage

class User < ActiveRecord::Base
  validates :email, db_uniqueness: true
  # The same as following:
  # validates :email, uniqueness: {case_sensitive: true, allow_nil: true, allow_blank: false}
end

original = User.create(email: 'email@mail.com')
dupe = User.create(email: 'email@mail.com')
# => false
dupe.errors.messages
# => {:email=>["has already been taken"]}
User.create!(email: 'email@mail.com')
# => ActiveRecord::RecordInvalid Validation failed: email has already been taken

Complete case_sensitive replacement example (for PostgreSQL only):

validates :slug, uniqueness: { case_sensitive: false, scope: :field }

Should be replaced by:

validates :slug, db_uniqueness: {index_name: :unique_index, case_sensitive: false, scope: :field}

Keep in mind: because valid? method uses default validator you should:

• if your index has many fields, provide proper scope option
• if your index has lower function, provide case_sensitive option
• if your index has where condition, provide proper where option

Problem

Unfortunately, ActiveRecord's validates_uniqueness_of approach does not ensure uniqueness. For example, we can skip validations or create two records in parallel queries. After that, our database becomes inconsistent because we assume some uniqueness over the table but it has duplicates.

validates_db_uniqueness_of solves the problem using unique index constraints in the database also providing backward compatibility with nice validations errors.

Advantages

• Ensures uniqueness because it uses unique constraints.
• Checks the existence of proper unique index at the boot time. Use ENV['SKIP_DB_UNIQUENESS_VALIDATOR_INDEX_CHECK'] = 'true' if you want to skip it in some cases. (For example, when you run migrations.) Note: we skip it for the abstract classes.
• It's two times faster in average because it skips unnecessary SQL query. See benchmarks below for details.
• It has different modes so you can pick up the best for your needs.

Configuration options

Rescue option

The validation has an option :rescue with two values:

• :default (default option) that follows default ActiveRecord behavior. It respects validate: false option for save/save! (for example, this is being used for nested associations)
• :always that catches database constraint errors and turns them to ActiveRecord validations filling .errors properly.

You may want to use rescue: :always in case you save nested associations with accepts_nested_attributes_for helper and you want the validation to happen automatically when a user provides duplicated data in the same request.

Modes

There are 3 mode options:

• :optimized - the default one. In this mode it turns DB constraint exceptions into proper validation messages.
• :enhanced - a combination of the standard uniqueness validation and the db uniqueness validation. Runs a query first but also rescues from exception. The preferable mode for user-facing validations.
• :standard - in this mode works pretty much the same way as validates_uniqueness_of (except the index existence check).

Benchmark (code)

Testing (RSpec)

Add require database_validations/rspec/matchers' to your spec file.

validate_db_uniqueness_of

Example:

class User < ActiveRecord::Base
  validates_db_uniqueness_of :field, message: 'duplicate', where: '(some_field IS NULL)', scope: :another_field, index_name: :unique_index
end

describe 'validations' do
  subject { User }

  it { is_expected.to validate_db_uniqueness_of(:field).with_message('duplicate').with_where('(some_field IS NULL)').scoped_to(:another_field).with_index(:unique_index) }
end

Using with RuboCop

DatabaseValidations provides custom cops for RuboCop to help you consistently apply the improvements. To use all of them, use rubocop --require database_validations/rubocop/cops or add to your .rubocop.yml file:

require:
  - database_validations/rubocop/cops

Or you case use some specific cop directly:

require:
  - database_validations/rubocop/cop/belongs_to
  - database_validations/rubocop/cop/uniqueness_of

Development

You need to have installed and running postgresql and mysql. And for each adapter manually create a database called database_validations_test accessible by your local user.

Then, run rake spec to run the tests.

To check the conformance with the style guides, run:

rubocop

To run benchmarks, run:

ruby -I lib benchmarks/composed_benchmarks.rb

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the DatabaseValidations project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.

Contributors

• Evgeniy Demin (author)
• Filipp Pirozhkov
• Maxim Krizhanovski
• Alfonso Uceda