graphql_preloader

What's this gem do

preload ActiveRecord Associations when using graphql and ActiveRecord

Install

gem 'graphql_preloader'

Scene

Your original code of resolver might look like this:

class Resolvers::ProfileResolver < GraphQL::Function
  description 'User profile'

  type Types::ProfileType

  def _call(_, args, ctx)
    ctx[:current_user]
  end
end

If the query like this:

query{
  profile{
    id
    works{
      comments{
        replyUser{
          name
        }
        content
      }
      name
      id
      likes{
        owner{
          name
          works{
            name
            likes{
              owner{
                name
              }
            }
          }
        }
      }
    }
    name
  }
}

It will cause Multi-level nested N + 1 problem.

And you want to resolve it, you can write like this:

class Resolvers::ProfileResolver < GraphQL::Function
  description 'User profile'

  type Types::ProfileType

  def _call(_, args, ctx)
    User.includes([works: [comments: :reply_user, likes: [owner: [works: [likes: :owner]]]]]).find(ctx[:current_user].id)
  end
end

You will manually resolve N + 1 problem in every resolver.Worse, even if only one field is used, you need to request all the tables included.

Usage

Your Resolver inherits from PreloadFunction instead of GraphQL::Function. Defining _call method instead of call Using included_model(your_model_name) instead of your original includes statement.

class Resolvers::ProfileResolver < PreloadFunction
  description 'User profile'

  type Types::ProfileType

  def _call(_, args, ctx)
    included_model(User).find(ctx[:current_user].id)
  end
end