by ConsultingMD

ConsultingMD / graphql-preload

Preload ActiveRecord associations with graphql-batch

128 Stars 44 Forks Last release: over 2 years ago (v2.0.1) MIT License 49 Commits 7 Releases

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Gem Version

Provides a DSL for the

gem that allows ActiveRecord associations to be preloaded in field definitions. Based on a gist by @theorygeek.


Add this line to your application's Gemfile:

gem 'graphql-preload'

And then execute:

$ bundle

Or install it yourself as:

$ gem install graphql-preload


First, enable preloading in your

Schema = GraphQL::Schema.define do
  use GraphQL::Batch

enable_preloading end


when defining your field:
PostType = GraphQL::ObjectType.define do
  name 'Post'

field :comments, !types[!CommentType] do # Post.includes(:comments) preload :comments

# Post.includes(:comments, :authors)
preload [:comments, :authors]

# Post.includes(:comments, authors: [:followers, :posts])
preload [:comments, { authors: [:followers, :posts] }]

resolve ->(obj, args, ctx) { obj.comments }

end end


Starting with Rails 4.1, you can scope your preloaded records by passing a valid scope to

. Scoping can improve performance by reducing the number of models to be instantiated and can help with certain business goals (e.g., only returning records that have not been soft deleted).

This functionality is surfaced through the

PostType = GraphQL::ObjectType.define do
  name 'Post'

field :comments, !types[!CommentType] do preload :comments preload_scope ->(args, ctx) { Comment.where(deleted_at: nil) }

# Resolves with records returned from the following query:
# SELECT "comments".*
# FROM "comments"
# WHERE "comments"."deleted_at" IS NULL
#   AND "comments"."post_id" IN (1, 2, 3)
resolve ->(obj, args, ctx) { obj.comments }

end end


After checking out the repo, run

to install dependencies. Then, run
rake test
to run the tests. You can also run
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
, and then run
bundle exec rake release
, which will create a git tag for the version, push git commits and tags, and push the
file to


Bug reports and pull requests are welcome on GitHub at


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

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