DatabaseValidations

ActiveRecord provides validations on app level but it won't guarantee the consistent. In some cases, like validates_uniqueness_of it executes additional SQL query to the database and that is not very efficient.

The main goal of the gem is to provide compatibility between database constraints and ActiveRecord validations with better performance and consistency.

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

validates_db_uniqueness_of

Supported databases: postgresql, mysql and sqlite.

Pros and Cons

Advantages:

  • Provides true uniqueness on the database level because it handles race conditions cases properly.
  • Check the existence of correct unique index at the boot time.
  • It's faster. See Benchmark section for details.

Disadvantages:

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

    class User < ActiveRecord::Base
  validates_db_uniqueness_of :email
  validates_db_uniqueness_of :name
end

original = User.create(name: 'name', email: '[email protected]')
dupe = User.create(name: 'name', email: '[email protected]')
# => false
dupe.errors.messages
# => {:name=>["has already been taken"]}

How it works?

We override save and save! methods where we rescue ActiveRecord::RecordNotUnique and add proper errors for compatibility.

For valid? we use implementation from validates_uniqueness_of where we query the database.

Usage

class User < ActiveRecord::Base
  validates_db_uniqueness_of :email
end

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

Configuration options

We want to provide full compatibility with existing validates_uniqueness_of validator.

This list of supported options from validates_uniqueness_of validator:

  • scope: One or more columns by which to limit the scope of the uniqueness constraint.
  • message: Specifies a custom error message (default is: "has already been taken").

Keep in mind: Even when we don't support case_sensitive, allow_nil and allow_blank options now, the following:

validates_db_uniqueness_of :email

Is the same by default as following 

validates_uniqueness_of :email, allow_nil: true, allow_blank: false, case_sensitive: true

The list of options to add support:

  • conditions: Specify the conditions to be included as a WHERE SQL fragment to limit the uniqueness constraint lookup (e.g. conditions: -> { where(status: 'active') }).
  • case_sensitive: Looks for an exact match. Ignored by non-text columns (true by default).
  • allow_nil: If set to true, skips this validation if the attribute is nil (default is false).
  • allow_blank: If set to true, skips this validation if the attribute is blank (default is false).
  • if: Specifies a method, proc or string to call to determine if the validation should occur (e.g. if: :allow_validation, or if: Proc.new { |user| user.signup_step > 2 }). The method, proc or string should return or evaluate to a true or false value.
  • unless: Specifies a method, proc or string to call to determine if the validation should not occur (e.g. unless: :skip_validation, or unless: Proc.new { |user| user.signup_step <= 2 }). The method, proc or string should return or evaluate to a true or false value.

Benchmark (code)

Case Validator SQLite PostgreSQL MySQL
Save duplicate item only validates_db_uniqueness_of 1.404k (±14.7%) i/s - 6.912k in 5.043409s 508.889 (± 2.8%) i/s - 2.550k in 5.015044s 649.356 (±11.5%) i/s - 3.283k in 5.153444s
validates_uniqueness_of 1.505k (±14.6%) i/s - 7.448k in 5.075696s 637.017 (±14.1%) i/s - 3.128k in 5.043434s 473.561 (± 9.7%) i/s - 2.352k in 5.021151s
Save unique item only validates_db_uniqueness_of 3.241k (±18.3%) i/s - 15.375k in 5.014244s 1.345k (± 5.5%) i/s - 6.834k in 5.096706s 1.439k (±12.9%) i/s - 7.100k in 5.033603s
validates_uniqueness_of 2.002k (±10.9%) i/s - 9.900k in 5.018449s 667.100 (± 4.8%) i/s - 3.350k in 5.034451s 606.334 (± 4.9%) i/s - 3.068k in 5.072587s
Each hundredth item is duplicate validates_db_uniqueness_of 3.534k (± 5.6%) i/s - 17.748k in 5.039277s 1.351k (± 6.5%) i/s - 6.750k in 5.017280s 1.436k (±11.6%) i/s - 7.154k in 5.062644s
validates_uniqueness_of 2.121k (± 6.8%) i/s - 10.653k in 5.049739s 658.199 (± 6.1%) i/s - 3.350k in 5.110176s 596.024 (± 6.7%) i/s - 2.989k in 5.041497s

Development

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

After checking out the repo, run bin/setup to install dependencies.

Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

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.

Authors