fix balances query n+1

app/graphql/sources/active_record.rb

@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+module Sources
+  class ActiveRecord < GraphQL::Dataloader::Source
+    # rubocop:disable Lint/MissingSuper
+    def initialize(model_class)
+      @model_class = model_class
+    end
+
+    def fetch(ids)
+      @model_class
+        .where(id: ids)
+        .index_by(&:id)
+        .slice(*ids)
+        .values
+    end
+  end
+end

app/graphql/types/balance_type.rb

@@ -7,7 +7,11 @@ module Types
     graphql_name "Balance"
 
     field :id, ID, null: false
-    field :currency, CurrencyType, null: false
     field :amount, String, null: false
+
+    field :currency, CurrencyType, null: false
+    def currency
+      dataloader.with(Sources::ActiveRecord, Currency).load(object.currency_id)
+    end
   end
 end

app/graphql/x_stake_schema.rb

@@ -2,6 +2,7 @@
 class XStakeSchema < GraphQL::Schema
   # mutation(Types::MutationType)
   query(Types::QueryType)
+  use GraphQL::Dataloader
 
   def self.resolve_type(abstract_type, obj, ctx)
     case obj