Rewrite N+1 query

Author: dlackty

lib/active_admin/sortable_tree/controller_actions.rb

@@ -24,10 +24,12 @@ def sortable(options = {})
       collection_action :sort, :method => :post do
         resource_name = ActiveAdmin::SortableTree::Compatibility.normalized_resource_name(active_admin_config.resource_name)
 
+        # Query all resources at once to avoid N+1
+        resources = Hash[resource_class.where(id: params[resource_name].keys).map { |r| [r.id, r] }]
+
         records = []
         params[resource_name].each_pair do |resource, parent_resource|
-          parent_resource = resource_class.find(parent_resource) rescue nil
-          records << [resource_class.find(resource), parent_resource]
+          records << [resources[resource], resources[parent_resource]]
         end
 
         errors = []