Sequel::Plugins::JsonapiEager

DEPRECATION NOTICE: This gem is deprecated in favor of the tactical_eager_loading Sequel plugin. It solves all of the eager loading automatically, and it also reuses reciprocal associations which eliminates DoSing. And it's general so it can be also used outside of JSON APIs.

This Sequel plugin enables you to dynamically eager load associations of objects you're exposing for your JSON API.

The JSON-API specification introduces the ability for clients to choose which associations they want to include in the response:

GET /users?include=quizzes.questions,posts

You as an author of the API want to eager load those associations, to avoid N+1 queries. However, Sequel has a slighly different API for eager loading associations:

User.eager(:quizzes => :questions).eager(:posts)

This plugin translates the JSON-API include format into Sequel.

gem 'sequel-jsonapi_eager'

This plugin exposes the jsonapi_eager method to your Sequel objects, to which you can pass in the include query parameter.

User.plugin :jsonapi_eager

users = User.jsonapi_eager("quizzes.questions,posts")
# translates into `User.eager(:quizzes => :questions).eager(:posts)`

users.all
# SELECT * FROM `users`
# SELECT * FROM `quizzes` WHERE (`quizzes`.`user_id` IN (3, 54, 5))
# SELECT * FROM `questions` WHERE (`questions`.`quiz_id` IN (2, 17, 19, 43))
# SELECT * FROM `posts` WHERE (`posts`.`user_id` IN (3, 54, 5))

You can also use this method in the dataset:

User.active.jsonapi_eager("quizzes.questions,posts")

What this plugin also gives you, which was the non-trivial part of the plugin, is the ability to eager load associations on model instances.

user = User[user_id]
user.jsonapi_eager("quizzes.questions,posts")

You need this when exposing single resources in your API, because you need to determine what to eager load at serialization time, at which point you only have the instance. Moreover, Sequel removes the eager loading when you fetch single records, so the following doesn't work:

user = User.eager(:quizzes => :questions)[user_id]
user # Doesn't contain the eager loading anymore
user.quizzes.map(&:questions) # N+1 query

This plugins helps you make very flexible APIs, while still keeping the performance tip-top.

MIT