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