GraphQL::ActiveRecordBatcher

GraphQL::ActiveRecordBatcher is a toolkit to batch record loading as well as preload ActiveRecord association durings GraphQL Execution.

It is meant to be used with the graphql gem and uses graphql-batch under the hood to preload and batch calls to your database.

Installation

Add this line to your application's Gemfile:

gem 'graphql-active_record_batcher'

And then execute:

$ bundle

Or install it yourself as:

$ gem install graphql-active_record_batcher

Usage

Set up preloading for a Schema

Schema = GraphQL::Schema.define do
  # Enable preloading on a per-schema basis
  enable_active_record_batching
  query Query
  mutation Mutation
end

Preloading Associations

Using GraphQL without preloading associations results in under performant API and too many queries to the database. Take for example a Movie type which has a characters associations, and this GraphQL query:

query {
  movie(id: "1") {
    characters {
      name
    }
  }
  movie(id: "2") {
    characters {
      name
    }
  }
}

This query would result in 4 calls to your database:

1: SELECT  "movies".* FROM "movies" WHERE "movies"."id" = ? LIMIT ?  [["id", 1]
2: SELECT  "movies".* FROM "movies" WHERE "movies"."id" = ? LIMIT ?  [["id", 2]
3: SELECT  "characters".* FROM "characters" WHERE "characters"."movie_id" = ? [["movie_id", 1]
4: SELECT  "characters".* FROM "characters" WHERE "characters"."movie_id" = ? [["movie_id", 2]

GraphQL::ActiveRecordBatcher lets you preload associations by using the preload definition during field definition:

StarWarsMovie = GraphQL::ObjectType.define do
  name "StarWarsMovie"
  description "A StarWars Movie"

  # Define which active record model represents
  # the parent object
  model Movie

  field :characters, !types[!Character] do
    preloads :characters
    resolve ->(movie, _, _) { movie.characters }
  end
end

Associations will now be preloaded and only 3 queries are used this time:

1: SELECT  "movies".* FROM "movies" WHERE "movies"."id" = ? LIMIT ?  [["id", 1]
2: SELECT  "movies".* FROM "movies" WHERE "movies"."id" = ? LIMIT ?  [["id", 2]
3: SELECT   "characters".* FROM "characters" WHERE "characters"."movie_d" IN (1, 2)

Preload multiple associations

If a certain call loads more than one association, you can use an array to express the ones to preload.

field :characters, !types[!Character] do
  preloads [:characters, :planets]
  resolve ->(movie, _, _) { movie.characters }
end

TODO

• [ ] Expose a way to batch finds
• [ ] Expose a way or documentation on how to batch the node field
• [x] Accept an array of preloads
• [ ] Accept nested preloads

License

The gem is available as open source under the terms of the MIT License.