AR::Sequence

Add support for PostgreSQL's SEQUENCE on ActiveRecord migrations.

Installation

Add this line to your application's Gemfile:

gem "ar-sequence"

And then execute:

$ bundle

Or install it yourself as:

$ gem install ar-sequence

Usage

To create a SEQUENCE, just use the method create_sequence.

class CreateUsers < ActiveRecord::Migration[5.2]
  def up
    create_sequence :position
  end

  def down
    drop_sequence :position
  end
end

You can also specify the initial value and increment:

create_sequence :position, increment: 2
create_sequence :position, start: 100

To define a column that has a sequence as its default value, use something like the following:

class CreateThings < ActiveRecord::Migration[5.2]
  def change
    create_sequence :position

    create_table :things do |t|
      t.text :name

      # PostgreSQL uses bigint as the sequence's default type.
      # Use a block to specify the default value on migrations.
      t.bigint :position,
                null: false,
                default: -> { "nextval('position')" }

      t.timestamps
    end
  end
end

This gem also adds a few helpers to interact with SEQUENCEs.

ActiveRecord::Base.nextval("position")       # Advance sequence and return new value
ActiveRecord::Base.currval("position")       # Return value most recently obtained with nextval for specified sequence.
ActiveRecord::Base.setval("position", 1234)  # Set sequence's current value

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test 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 at https://github.com/fnando/ar-sequence. 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.