Fix performance on instances list in admin UI (#15282)

- Reduce duplicate queries
- Remove n+1 queries
- Add accounts count to detailed view
- Add separate action log entry for updating existing domain blocks

app/controllers/admin/instances_controller.rb

@@ -2,65 +2,31 @@
 
 module Admin
   class InstancesController < BaseController
-    before_action :set_domain_block, only: :show
-    before_action :set_domain_allow, only: :show
+    before_action :set_instances, only: :index
     before_action :set_instance, only: :show
 
     def index
       authorize :instance, :index?
-
-      @instances = ordered_instances
     end
 
     def show
       authorize :instance, :show?
-
-      @following_count = Follow.where(account: Account.where(domain: params[:id])).count
-      @followers_count = Follow.where(target_account: Account.where(domain: params[:id])).count
-      @reports_count   = Report.where(target_account: Account.where(domain: params[:id])).count
-      @blocks_count    = Block.where(target_account: Account.where(domain: params[:id])).count
-      @available       = DeliveryFailureTracker.available?(params[:id])
-      @media_storage   = MediaAttachment.where(account: Account.where(domain: params[:id])).sum(:file_file_size)
-      @private_comment = @domain_block&.private_comment
-      @public_comment  = @domain_block&.public_comment
     end
 
     private
 
-    def set_domain_block
-      @domain_block = DomainBlock.rule_for(params[:id])
-    end
-
-    def set_domain_allow
-      @domain_allow = DomainAllow.rule_for(params[:id])
-    end
-
     def set_instance
-      resource   = Account.by_domain_accounts.find_by(domain: params[:id])
-      resource ||= @domain_block
-      resource ||= @domain_allow
+      @instance = Instance.find(params[:id])
+    end
 
-      if resource
-        @instance = Instance.new(resource)
-      else
-        not_found
-      end
+    def set_instances
+      @instances = filtered_instances.page(params[:page])
     end
 
     def filtered_instances
       InstanceFilter.new(whitelist_mode? ? { allowed: true } : filter_params).results
     end
 
-    def paginated_instances
-      filtered_instances.page(params[:page])
-    end
-
-    helper_method :paginated_instances
-
-    def ordered_instances
-      paginated_instances.map { |resource| Instance.new(resource) }
-    end
-
     def filter_params
       params.slice(*InstanceFilter::KEYS).permit(*InstanceFilter::KEYS)
     end