Cached ActiveRecord Connection

relation_cache.rb

require "bundler/inline"

gemfile do
  gem "graphql"
  gem "graphql-pro"
  gem "sqlite3"
  gem "rails"
end
require "rails/all"
require "logger"

# I don't have `Rails.cache`, so I'm making one here:
$cache = ActiveSupport::Cache::MemoryStore.new

# Make a custom subclass of the built-in connection class, adding `cache.fetch` calls:
class CachedActiveRecordConnection < GraphQL::Pagination::ActiveRecordRelationConnection
  def sliced_nodes
    @sliced_nodes ||= begin
      nodes = super
      cache_key = nodes.to_sql
      $cache.fetch(cache_key) do
        nodes.to_a
      end
    end
  end

  def load_nodes
    @nodes ||= begin
      cache_key = limited_nodes.to_sql
      $cache.fetch(cache_key) do
        limited_nodes.to_a
      end
    end
  end
end

# Make a schema with "searchable" books:
class MySchema < GraphQL::Schema
  class Book < GraphQL::Schema::Object
    field :author, String
    field :title, String
  end

  class Query < GraphQL::Schema::Object
    field :books, Book.connection_type do
      argument :query, String, required: false
    end

    def books(query:)
      # Manually apply the custom connection class:
      CachedActiveRecordConnection.new(::Book.where("LOWER(title || ' ' || author) LIKE ?", "%#{query.downcase}%"))
    end
  end

  query(Query)
end

# Set up the database and add some records:
ActiveRecord::Base.establish_connection(adapter: "sqlite3", database: ":memory:")
ActiveRecord::Schema.define do
  self.verbose = false
  create_table :books, force: true do |t|
    t.column :author, :string
    t.column :title, :string
  end
end
class Book < ActiveRecord::Base; end
Book.create!(title: "Remembering", author: "Wendell Berry")
Book.create!(title: "The Going to Bed Book", author: "Sandra Boynton")
Book.create!(title: "Gilead", author: "Marilynne Robinson")
Book.create!(title: "Historical Brewing Techniques", author: "Lars Marius Garshol")
Book.create!(title: "The Tale of Tom Kitten", author: "Beatrix Potter")

ActiveRecord::Base.logger = Logger.new(STDOUT)

# Now run some queries. Only the first one of each pair should emit a message to the Logger:
puts "First execution:"
pp MySchema.execute("{ books(query: \"be\") { nodes { title author }} }").to_h
puts "Second execution:"
pp MySchema.execute("{ books(query: \"be\") { nodes { title author }} }").to_h


puts "\n\nFirst execution with pagination:"
pp MySchema.execute("{ books(query: \"be\", first: 2) { nodes { title author } } }").to_h
puts "Second execution with pagination:"
res = MySchema.execute("{ books(query: \"be\", first: 2) { nodes { title author } pageInfo { endCursor } } }").to_h
pp res

next_cursor = res["data"]["books"]["pageInfo"]["endCursor"]
puts "\n\nFirst execution with just pageInfo:"
pp MySchema.execute("{ books(query: \"be\", first: 1, after: #{next_cursor.inspect}) { pageInfo { hasNextPage } } }").to_h
puts "Second execution with just pageInfo:"
pp MySchema.execute("{ books(query: \"be\", first: 1, after: #{next_cursor.inspect}) { pageInfo { hasNextPage } } }").to_h

# First execution:
# D, [2022-01-28T13:18:15.875212 #52824] DEBUG -- :   Book Load (0.1ms)  SELECT "books".* FROM "books" WHERE (LOWER(title || ' ' || author) LIKE '%be%') LIMIT -1 OFFSET ?  [["OFFSET", 0]]
# {"data"=>
#   {"books"=>
#     {"nodes"=>
#       [{"title"=>"Remembering", "author"=>"Wendell Berry"},
#        {"title"=>"The Going to Bed Book", "author"=>"Sandra Boynton"},
#        {"title"=>"The Tale of Tom Kitten", "author"=>"Beatrix Potter"}]}}}
# Second execution:
# {"data"=>
#   {"books"=>
#     {"nodes"=>
#       [{"title"=>"Remembering", "author"=>"Wendell Berry"},
#        {"title"=>"The Going to Bed Book", "author"=>"Sandra Boynton"},
#        {"title"=>"The Tale of Tom Kitten", "author"=>"Beatrix Potter"}]}}}


# First execution with pagination:
# D, [2022-01-28T13:18:15.885540 #52824] DEBUG -- :   Book Load (0.7ms)  SELECT "books".* FROM "books" WHERE (LOWER(title || ' ' || author) LIKE '%be%') LIMIT ? OFFSET ?  [["LIMIT", 2], ["OFFSET", 0]]
# {"data"=>
#   {"books"=>
#     {"nodes"=>
#       [{"title"=>"Remembering", "author"=>"Wendell Berry"},
#        {"title"=>"The Going to Bed Book", "author"=>"Sandra Boynton"}]}}}
# Second execution with pagination:
# {"data"=>
#   {"books"=>
#     {"nodes"=>
#       [{"title"=>"Remembering", "author"=>"Wendell Berry"},
#        {"title"=>"The Going to Bed Book", "author"=>"Sandra Boynton"}],
#      "pageInfo"=>{"endCursor"=>"Mg"}}}}


# First execution with just pageInfo:
# D, [2022-01-28T13:18:15.892276 #52824] DEBUG -- :   Book Load (0.1ms)  SELECT "books".* FROM "books" WHERE (LOWER(title || ' ' || author) LIKE '%be%') LIMIT -1 OFFSET ?  [["OFFSET", 2]]
# {"data"=>{"books"=>{"pageInfo"=>{"hasNextPage"=>true}}}}
# Second execution with just pageInfo:
# {"data"=>{"books"=>{"pageInfo"=>{"hasNextPage"=>true}}}}