Use GraphQL Batch for find by id fields

Gemfile

@@ -7,12 +7,11 @@ end
 
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.0.1'
-# use PG in prod for heroku
-gem 'pg'
 # Use Puma as the app server
 gem 'puma', '~> 3.0'
 # Use GraphQL!
 gem 'graphql', '~> 1.4.3'
+gem 'graphql-batch'
 # GraphiQL Interface
 gem 'graphiql-rails', '~> 1.4.1'
 
@@ -24,6 +23,10 @@ group :development, :test do
   gem 'sqlite3'
 end
 
+group :production do
+  gem 'pg'
+end
+
 group :development do
   # Access an IRB console on exception pages or by using <%= console %> anywhere in the code.
   gem 'web-console', '>= 3.3.0'

Gemfile.lock

@@ -51,6 +51,9 @@ GEM
     graphiql-rails (1.4.1)
       rails
     graphql (1.4.3)
+    graphql-batch (0.3.1)
+      graphql (>= 0.8, < 2)
+      promise.rb (~> 0.7.2)
     i18n (0.8.0)
     json (2.0.2)
     listen (3.0.8)
@@ -70,6 +73,7 @@ GEM
     nokogiri (1.7.0.1)
       mini_portile2 (~> 2.1.0)
     pg (0.19.0)
+    promise.rb (0.7.2)
     puma (3.7.0)
     rack (2.0.1)
     rack-test (0.6.3)
@@ -137,6 +141,7 @@ DEPENDENCIES
   byebug
   graphiql-rails (~> 1.4.1)
   graphql (~> 1.4.3)
+  graphql-batch
   listen (~> 3.0.5)
   pg
   puma (~> 3.0)

app/models/graph.rb

@@ -0,0 +1,17 @@
+module Graph
+  class << self
+    def find_by_id_field(type, model)
+      GraphQL::Field.define do
+        type type
+        argument :id, !types.ID
+        resolve ->(_, args, _) do
+          gid = GlobalID.parse(args[:id])
+
+          return unless gid.model_name == type.name
+
+          Graph::FindLoader.for(model).load(gid.model_id.to_i)
+        end
+      end
+    end
+  end
+end

app/models/graph/find_loader.rb

@@ -0,0 +1,11 @@
+class Graph::FindLoader < GraphQL::Batch::Loader
+  def initialize(model)
+    @model = model
+  end
+
+  def perform(ids)
+    records = @model.where(id: ids.uniq)
+    records.each { |record| fulfill(record.id, record) }
+    ids.each { |id| fulfill(id, nil) unless fulfilled?(id) }
+  end
+end

app/models/graph/schema.rb

@@ -19,5 +19,8 @@ module Graph
 
       Object.const_get(gid.model_name).find(gid.model_id)
     end
+
+    lazy_resolve(Promise, :sync)
+    instrument(:query, GraphQL::Batch::Setup)
   end
 end

app/models/graph/types/query.rb

@@ -8,56 +8,32 @@ module Types
       field :node, GraphQL::Relay::Node.field
       field :nodes, GraphQL::Relay::Node.plural_field
 
-      field :person, Graph::Types::Person do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Person.find_by(id: args['id']) }
-      end
-
+      field :person, Graph.find_by_id_field(Graph::Types::Person, ::Person)
       field :people, types[Graph::Types::Person] do
         resolve ->(_, _, _) { ::Person.all }
       end
 
-      field :planet, Graph::Types::Planet do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Planet.find(args['id']) }
-      end
-
+      field :planet, Graph.find_by_id_field(Graph::Types::Planet, ::Planet)
       field :planets, types[Graph::Types::Planet] do
         resolve ->(_, _, _) { ::Planet.all }
       end
 
-      field :film, Graph::Types::Film do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Film.find(args['id']) }
-      end
-
+      field :film, Graph.find_by_id_field(Graph::Types::Film, ::Film)
       field :films, types[Graph::Types::Film] do
         resolve ->(_, _, _) { ::Film.all }
       end
 
-      field :species, Graph::Types::Species do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Species.find(args['id']) }
-      end
-
+      field :species, Graph.find_by_id_field(Graph::Types::Species, ::Species)
       field :allSpecies, types[Graph::Types::Species] do
         resolve ->(_, _, _) { ::Species.all }
       end
 
-      field :starship, Graph::Types::Starship do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Starship.find(args['id']) }
-      end
-
+      field :starship, Graph.find_by_id_field(Graph::Types::Starship, ::Starship)
       field :starships, types[Graph::Types::Starship] do
         resolve ->(_, _, _) { ::Starship.all }
       end
 
-      field :vehicle, Graph::Types::Vehicle do
-        argument :id, types.ID
-        resolve ->(_, args, _) { ::Vehicle.find(args['id']) }
-      end
-
+      field :vehicle, Graph.find_by_id_field(Graph::Types::Vehicle, ::Vehicle)
       field :vehicles, types[Graph::Types::Vehicle] do
         resolve ->(_, _, _) { ::Vehicle.all }
       end

config/secrets.yml

@@ -1,8 +1,8 @@
 development:
-  secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>
+  secret_key_base: secret-for-development-not-so-secret
 
 test:
-  secret_key_base:  <%= ENV["SECRET_KEY_BASE"] %>
+  secret_key_base: secret-for-test-not-so-secret
 
 production:
   secret_key_base: <%= ENV["SECRET_KEY_BASE"] %>

test/controllers/graphql_controller_test.rb

@@ -113,7 +113,7 @@ class GraphQLControllerTest < ActionDispatch::IntegrationTest
 
   def full_graphql_query
     "
-      query Full($personID: ID, $filmID: ID, $planetID: ID, $starshipID: ID, $speciesID: ID, $vehicleID: ID) {
+      query Full($personID: ID!, $filmID: ID!, $planetID: ID!, $starshipID: ID!, $speciesID: ID!, $vehicleID: ID!) {
         person(id: $personID) {
           birthYear
           eyeColor
@@ -204,12 +204,12 @@ def default_variables
     vehicle = vehicles(:snowspeeder)
 
     {
-      "starshipID" => starship.id,
-      "personID" => person.id,
-      "filmID" => film.id,
-      "planetID" => planet.id,
-      "speciesID" => species.id,
-      "vehicleID" => vehicle.id
+      "starshipID" => starship.to_global_id,
+      "personID" => person.to_global_id,
+      "filmID" => film.to_global_id,
+      "planetID" => planet.to_global_id,
+      "speciesID" => species.to_global_id,
+      "vehicleID" => vehicle.to_global_id,
     }
   end
 end