ActiveRecord::Postgres::Constraints

From http://edgeguides.rubyonrails.org/active_record_migrations.html#types-of-schema-dumps:

There is however a trade-off: db/schema.rb cannot express database specific items such as triggers, stored procedures or check constraints. While in a migration you can execute custom SQL statements, the schema dumper cannot reconstitute those statements from the database. If you are using features like this, then you should set the schema format to :sql.

No longer is this the case. You can now use the default schema format (:ruby) and still preserve your check constraints.

At this time, this only supports check and exclude constraints for the postgresql ActiveRecord database adapter.

Usage

Add a check constraint

Add check constraints to a table in a migration:

create_table :people do |t|
  t.string :title
  t.check_constraint title: ['Mr.', 'Mrs.', 'Dr.']
end

OR

add_check_constraint :people, title: ['Mr.', 'Mrs.', 'Dr.']

Remove a check constraint

# If you don't need it to be reversible:
remove_check_constraint :people

# If you need it to be reversible (Recommended):
remove_check_constraint :people, title: ['Mr.', 'Mrs.', 'Dr.']

Add an exclude constraint

Add exclude constraints to a table in a migration:

create_table :booking do |t|
  t.integer :room_id
  t.datetime :from
  t.datetime :to
  t.exclude_constraint using: :gist, 'tsrange("from", "to")' => :overlaps, room_id: :equals
end

OR

add_exclude_constraint :booking, using: :gist, 'tsrange("from", "to")' => :overlaps, room_id: :equals

Remove an exclude constraint

# If you don't need it to be reversible:
remove_exclude_constraint :booking

# If you need it to be reversible (Recommended):
remove_exclude_constraint :booking, using: :gist, 'tsrange("from", "to")' => :overlaps, room_id: :equals

Constrainsts with custom conditions

If you need custom/complex conditions of any sort, you can even use string conditions:

create_table :people do |t|
  t.string :title
  t.check_constraint "title IS NULL OR title IN ['Mr.', 'Mrs.', 'Dr.']"
end

Installation

Add this line to your application's Gemfile:

gem 'active_record-postgres-constraints'

And then execute:

$ bundle

Testing

$ (cd spec/dummy && bin/rake db:create RAILS_ENV=test) # One time before running tests
$ bundle exec rspec # To run tests as often as you'd like

Contributing

If you're interested in building support for other database adapters, we welcome your contribution!

License

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