Add validations to your ActiveRecord models based on your database constraints.
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.

ActiveRecord::DatabaseValidations Build Status

Add validations to your ActiveRecord models based on your database constraints.

This gem is primarily intended for MySQL databases not running in strict mode, which can easily cause data loss. These problems are documented in DataLossTest

Should be thread-safe. Please submit an issue or PR if you can prove otherwise.


Add this line to your application's Gemfile:

gem 'activerecord-databasevalidations'

And then execute:

$ bundle

Or install it yourself as:

$ gem install activerecord-databasevalidations


You can use ActiveModel's validates method to define what fields you want to validate based on the database constraints.

class Foo < ActiveRecord::Base
  validates :boolean_field, database_constraints: :not_null
  validates :string_field, database_constraints: [:size, :basic_multilingual_plane]
  validates :decimal_field, :integer_field, database_constraints: :range

You can also use validates_database_constraints_of:

class Bar < ActiveRecord::Base
  validates_database_constraints_of :my_field, with: :size

Available validations

You have to specify what conatrints you want to validate for. Valid values are:

  • :range to validate the numeric range of a column based on it's type.
  • :size to validate for the size of textual and binary columns. It will pick character size or bytesize based on the column's type.
  • :basic_multilingual_plane to validate that all characters for text fields are inside the basic multilingual plane of unicode (unless you use the utf8mb4 character set).
  • :not_null to validate a NOT NULL contraint.

The validations will only be created if it makes sense for the column, e.g. a :not_null validation will only be added if the column has a NOT NULL constraint defined on it.

Hand-rolling validations

You can also instantiate the validators yourself:

class Bar < ActiveRecord::Base
  validates :string_field, bytesize: { maximum: 255 }, basic_multilingual_plane: true
  validates :string_field, not_null: true

Note that this will create validations without inspecting the column to see if it actually makes sense.

Replicating MySQL's truncation behavior

Sometimes, truncated a string that goes over the column's limit is the best option, if you don't want one field's value being too long prevent the record from saving.

You can use truncate_string to replicate MySQL's non-strict truncating behavior, so you can prepare yourself for eventually turning on strict mode.

class Unicorn < ActiveRecord::Base
  include ActiveRecord::DatabaseValidations::StringTruncator

  before_validation truncate_string(:string_field)
  validates :string_field, database_constraints: [:size]

In this example, it will truncate the string to a size that will fit before validation, so the subsequent size validation will now always pass.


  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 new Pull Request