ActiveRecord::Sequence

Access to PostgreSQL's Sequences

Installation

Add this line to your application's Gemfile:

gem 'active_record-sequence'

And then execute:

$ bundle

Or install it yourself as:

$ gem install active_record-sequence

Usage

By default new sequence starts from 1:

sequence = ActiveRecord::Sequence.create('numbers')

#next returns next value in the sequence:

sequence.next #=> 1
sequence.next #=> 2

#peek returns current value:

sequence.peek #=> 2

You can start a sequence with specific value:

sequence = ActiveRecord::Sequence.create('numbers', start: 42)
sequence.next #=> 42
sequence.next #=> 43

Specify custom increment value:

sequence = ActiveRecord::Sequence.create('numbers', increment: 3)
sequence.next #=> 1
sequence.next #=> 4

If you pass negative increment, a sequence will be decreasing:

sequence = ActiveRecord::Sequence.create('numbers', increment: -3)
sequence.next #=> -1
sequence.next #=> -4

To limit number of elements in a sequence specify max value:

sequence = ActiveRecord::Sequence.create('numbers', max: 2)
sequence.next #=> 1
sequence.next #=> 2
sequence.next #=> fail with StopIteration

Decreasing sequence may be limited as well:

sequence = ActiveRecord::Sequence.create('numbers', min: -2, increment: -1)
sequence.next #=> -1
sequence.next #=> -2
sequence.next #=> fail with StopIteration

To define infinite sequence, use cycle option:

sequence = ActiveRecord::Sequence.create('numbers', max: 2, cycle: true)
sequence.next #=> 1
sequence.next #=> 2
sequence.next #=> 1
sequence.next #=> 2
# etc.

You can use previously created sequence by instantiating Sequence class:

ActiveRecord::Sequence.create('numbers', max: 2, cycle: true)
sequence = ActiveRecord::Sequence.new('numbers')
sequence.next #=> 1
sequence.next #=> 2
sequence.next #=> 1

To destroy a sequence:

ActiveRecord::Sequence.drop('numbers')

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake 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/bolshakov/active_record-sequence.