PERF: Fix N+1 queries when loading groups.

app/serializers/basic_group_serializer.rb

@@ -11,10 +11,7 @@ class BasicGroupSerializer < ApplicationSerializer
              :title,
              :grant_trust_level,
              :incoming_email,
-             :notification_level,
              :has_messages,
-             :is_member,
-             :mentionable,
              :flair_url,
              :flair_bg_color,
              :flair_color
@@ -22,30 +19,4 @@ class BasicGroupSerializer < ApplicationSerializer
   def include_incoming_email?
     scope.is_staff?
   end
-
-  def notification_level
-    fetch_group_user&.notification_level
-  end
-
-  def include_notification_level?
-    scope.authenticated?
-  end
-
-  def mentionable
-    object.mentionable?(scope.user, object.id)
-  end
-
-  def is_member
-    scope.is_admin? || fetch_group_user.present?
-  end
-
-  def include_is_member?
-    scope.authenticated?
-  end
-
-  private
-
-  def fetch_group_user
-    @group_user ||= object.group_users.find_by(user_id: scope.user.id)
-  end
 end

app/serializers/basic_group_user_serializer.rb

@@ -0,0 +1,3 @@
+class BasicGroupUserSerializer < ApplicationSerializer
+  attributes :group_id, :user_id, :notification_level
+end

app/serializers/group_serializer.rb

@@ -0,0 +1,11 @@
+class GroupSerializer < BasicGroupSerializer
+  attributes :mentionable
+
+  def mentionable
+    object.mentionable?(scope.user, object.id)
+  end
+
+  def include_mentionable?
+    authenticated?
+  end
+end

app/serializers/group_show_serializer.rb

@@ -0,0 +1,11 @@
+class GroupShowSerializer < BasicGroupSerializer
+  attributes :is_group_user
+
+  def include_is_group_user?
+    scope.authenticated?
+  end
+
+  def is_group_user
+    object.users.include?(scope.user)
+  end
+end

app/serializers/user_serializer.rb

@@ -73,6 +73,7 @@ class UserSerializer < BasicUserSerializer
 
   has_one :invited_by, embed: :object, serializer: BasicUserSerializer
   has_many :groups, embed: :object, serializer: BasicGroupSerializer
+  has_many :group_users, embed: :object, serializer: BasicGroupUserSerializer
   has_many :featured_user_badges, embed: :ids, serializer: UserBadgeSerializer, root: :user_badges
   has_one  :card_badge, embed: :object, serializer: BadgeSerializer
   has_one :user_option, embed: :object, serializer: UserOptionSerializer
@@ -127,13 +128,19 @@ class UserSerializer < BasicUserSerializer
   end
 
   def groups
+    groups = object.groups.order(:id)
+
     if scope.is_admin? || object.id == scope.user.try(:id)
-      object.groups
+      groups
     else
-      object.groups.where(visible: true)
+      groups.where(visible: true)
     end
   end
 
+  def group_users
+    object.group_users.order(:group_id)
+  end
+
   def include_email?
     object.id && object.id == scope.user.try(:id)
   end