Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/derrickreimer/sequenced

Generate scoped sequential IDs for ActiveRecord models
https://github.com/derrickreimer/sequenced

activerecord ruby

Last synced: 5 days ago
JSON representation

Generate scoped sequential IDs for ActiveRecord models

Awesome Lists containing this project

README 

        
# Sequenced



[![.github/workflows/ci.yml](https://github.com/derrickreimer/sequenced/actions/workflows/ci.yml/badge.svg)](https://github.com/derrickreimer/sequenced/actions/workflows/ci.yml)

[![Code Climate](https://codeclimate.com/github/djreimer/sequenced.svg)](https://codeclimate.com/github/djreimer/sequenced)

[![Gem Version](https://badge.fury.io/rb/sequenced.svg)](http://badge.fury.io/rb/sequenced)



Sequenced is a simple gem that generates scoped sequential IDs for

ActiveRecord models. This gem provides an `acts_as_sequenced` macro that

automatically assigns a unique, sequential ID to each record. The sequential ID is

not a replacement for the database primary key, but rather adds another way to

retrieve the object without exposing the primary key.



## Purpose



It's generally a bad practice to expose your primary keys to the world

in your URLs. However, it is often appropriate to number objects in sequence

(in the context of a parent object).



For example, given a Question model that has many Answers, it makes sense

to number answers sequentially for each individual question. You can achieve

this with Sequenced in one line of code:



```ruby

class Question < ActiveRecord::Base

  has_many :answers

end



class Answer < ActiveRecord::Base

  belongs_to :question

  acts_as_sequenced scope: :question_id

end

```



## Installation



Add the gem to your Gemfile:



    gem 'sequenced'



Install the gem with bundler:



    bundle install



## Usage



To add a sequential ID to a model, first add an integer column called

`sequential_id` to the model (or you many name the column anything you

like and override the default). For example:



    rails generate migration add_sequential_id_to_answers sequential_id:integer

    rake db:migrate



Then, call the `acts_as_sequenced` macro in your model class:



```ruby

class Answer < ActiveRecord::Base

  belongs_to :question

  acts_as_sequenced scope: :question_id

end

```



The `scope` option can be any attribute, but will typically be the foreign

key of an associated parent object. You can even scope by multiple columns

for polymorphic relationships:



```ruby

class Answer < ActiveRecord::Base

  belongs_to :questionable, :polymorphic => true

  acts_as_sequenced scope: [:questionable_id, :questionable_type]

end

```



Multiple sequences can be defined by using the macro multiple times:



```ruby

class Answer < ActiveRecord::Base

  belongs_to :account

  belongs_to :question



  acts_as_sequenced column: :question_answer_number, scope: :question_id

  acts_as_sequenced column: :account_answer_number, scope: :account_id

end

```



## Schema and data integrity



**This gem is only concurrent-safe for PostgreSQL databases**. For other database systems, unexpected behavior may occur if you attempt to create records concurrently.



You can mitigate this somewhat by applying a unique index to your sequential ID column (or a multicolumn unique index on sequential ID and scope columns, if you are using scopes). This will ensure that you can never have duplicate sequential IDs within a scope, causing concurrent updates to instead raise a uniqueness error at the database-level.



It is also a good idea to apply a not-null constraint to your sequential ID column as well if you never intend to skip it.



Here is an example migration for a model that has a `sequential_id` scoped to a `burrow_id`:



```ruby

# app/db/migrations/20151120190645_create_badgers.rb

class CreateBadgers < ActiveRecord::Migration

  def change

    create_table :badgers do |t|

      t.integer :sequential_id, null: false

      t.integer :burrow_id

    end



    add_index :badgers, [:sequential_id, :burrow_id], unique: true

  end

end

```



If you are adding a sequenced column to an existing table, you need to account for that in your migration.



Here is an example migration that adds and sets the `sequential_id` column based on the current database records:

```ruby

# app/db/migrations/20151120190645_add_sequental_id_to_badgers.rb

class AddSequentalIdToBadgers < ActiveRecord::Migration

  add_column :badgers, :sequential_id, :integer



  execute <<~SQL

    UPDATE badgers

    SET sequential_id = old_badgers.next_sequential_id

    FROM (

      SELECT id, ROW_NUMBER()

      OVER(

        PARTITION BY burrow_id

        ORDER BY id

      ) AS next_sequential_id

      FROM badgers

    ) old_badgers

    WHERE badgers.id = old_badgers.id

  SQL



  change_column :badgers, :sequential_id, :integer, null: false

  add_index :badgers, [:sequential_id, :burrow_id], unique: true

end

```



## Configuration



### Overriding the default sequential ID column



By default, Sequenced uses the `sequential_id` column and assumes it already

exists. If you wish to store the sequential ID in different integer column,

simply specify the column name with the `column` option:



```ruby

acts_as_sequenced scope: :question_id, column: :my_sequential_id

```



### Starting the sequence at a specific number



By default, Sequenced begins sequences with 1. To start at a different

integer, simply set the `start_at` option:



```ruby

acts_as_sequenced start_at: 1000

```



You may also pass a lambda to the `start_at` option:



```ruby

acts_as_sequenced start_at: lambda { |r| r.computed_start_value }

```



### Indexing the sequential ID column



For optimal performance, it's a good idea to index the sequential ID column

on sequenced models.



### Skipping sequential ID generation



If you'd like to skip generating a sequential ID under certain conditions,

you may pass a lambda to the `skip` option:



```ruby

acts_as_sequenced skip: lambda { |r| r.score == 0 }

```



## Example



Suppose you have a question model that has many answers. This example

demonstrates how to use Sequenced to enable access to the nested answer

resource via its sequential ID.



```ruby

# app/models/question.rb

class Question < ActiveRecord::Base

  has_many :answers

end



# app/models/answer.rb

class Answer < ActiveRecord::Base

  belongs_to :question

  acts_as_sequenced scope: :question_id



  # Automatically use the sequential ID in URLs

  def to_param

    self.sequential_id.to_s

  end

end



# config/routes.rb

resources :questions do

  resources :answers

end



# app/controllers/answers_controller.rb

class AnswersController < ApplicationController

  def show

    @question = Question.find(params[:question_id])

    @answer = @question.answers.find_by(sequential_id: params[:id])

  end

end

```



Now, answers are accessible via their sequential IDs:



    http://example.com/questions/5/answers/1  # Good



instead of by their primary keys:



    http://example.com/questions/5/answer/32454  # Bad



## Contributing



1. Fork it

2. Create your feature branch (`git checkout -b my-new-feature`)

3. Commit your changes (`git commit -am 'Added some feature'`)

4. Push to the branch (`git push origin my-new-feature`)

5. Create new Pull Request