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