PERF: introduce fragment caches in site serializer

app/models/category.rb

@@ -193,7 +193,11 @@ SQL
   end
 
   def topic_url
-    topic_only_relative_url.try(:relative_url)
+    if has_attribute?("topic_slug")
+      Topic.relative_url(topic_id, topic_slug)
+    else
+      topic_only_relative_url.try(:relative_url)
+    end
   end
 
   def description_text

app/models/group.rb

@@ -15,6 +15,13 @@ class Group < ActiveRecord::Base
   after_save :update_primary_group
   after_save :update_title
 
+  after_save :expire_cache
+  after_destroy :expire_cache
+
+  def expire_cache
+    ApplicationSerializer.expire_cache_fragment!("group_names")
+  end
+
   validate :name_format_validator
   validates_uniqueness_of :name, case_sensitive: false
 

app/models/post_action_type.rb

@@ -1,7 +1,17 @@
 require_dependency 'enum'
+require_dependency 'distributed_cache'
 
 class PostActionType < ActiveRecord::Base
+  after_save :expire_cache
+  after_destroy :expire_cache
+
+  def expire_cache
+    ApplicationSerializer.expire_cache_fragment!("post_action_types")
+    ApplicationSerializer.expire_cache_fragment!("post_action_flag_types")
+  end
+
   class << self
+
     def ordered
       order('position asc')
     end

app/models/site.rb

@@ -13,14 +13,6 @@ class Site
     SiteSetting
   end
 
-  def post_action_types
-    PostActionType.ordered
-  end
-
-  def topic_flag_types
-    post_action_types.where(name_key: ['inappropriate', 'spam', 'notify_moderators'])
-  end
-
   def notification_types
     Notification.types
   end
@@ -29,10 +21,6 @@ class Site
     TrustLevel.all
   end
 
-  def groups
-    @groups ||= Group.order(:name).map { |g| { id: g.id, name: g.name } }
-  end
-
   def user_fields
     UserField.all
   end
@@ -41,7 +29,8 @@ class Site
     @categories ||= begin
       categories = Category
         .secured(@guardian)
-        .includes(:topic_only_relative_url)
+        .joins('JOIN topics t on t.id = categories.topic_id')
+        .select('categories.*, t.slug topic_slug')
         .order(:position)
 
       categories = categories.to_a
@@ -53,7 +42,9 @@ class Site
         end
       end
 
-      allowed_topic_create = Set.new(Category.topic_create_allowed(@guardian).pluck(:id))
+      allowed_topic_create_ids =
+        @guardian.anonymous? ? [] : Category.topic_create_allowed(@guardian).pluck(:id)
+      allowed_topic_create = Set.new(allowed_topic_create_ids)
 
       by_id = {}
 

app/models/topic.rb

@@ -736,12 +736,16 @@ class Topic < ActiveRecord::Base
     self.class.url id, slug, post_number
   end
 
-  def relative_url(post_number=nil)
+  def self.relative_url(id, slug, post_number=nil)
     url = "#{Discourse.base_uri}/t/#{slug}/#{id}"
     url << "/#{post_number}" if post_number.to_i > 1
     url
   end
 
+  def relative_url(post_number=nil)
+    Topic.relative_url(id, slug, post_number)
+  end
+
   def unsubscribe_url
     "#{url}/unsubscribe"
   end

app/serializers/site_serializer.rb

@@ -12,15 +12,35 @@ class SiteSerializer < ApplicationSerializer
              :is_readonly,
              :disabled_plugins,
              :user_field_max_length,
-             :suppressed_from_homepage_category_ids
+             :suppressed_from_homepage_category_ids,
+             :post_action_types,
+             :topic_flag_types
 
   has_many :categories, serializer: BasicCategorySerializer, embed: :objects
-  has_many :post_action_types, embed: :objects
-  has_many :topic_flag_types, serializer: TopicFlagTypeSerializer, embed: :objects
   has_many :trust_levels, embed: :objects
   has_many :archetypes, embed: :objects, serializer: ArchetypeSerializer
   has_many :user_fields, embed: :objects, serialzer: UserFieldSerializer
 
+  def groups
+    cache_fragment("group_names") do
+      Group.order(:name).pluck(:id,:name).map { |id,name| { id: id, name: name } }.as_json
+    end
+  end
+
+  def post_action_types
+    cache_fragment("post_action_types") do
+      ActiveModel::ArraySerializer.new(PostActionType.ordered).as_json
+    end
+  end
+
+  def topic_flag_types
+    cache_fragment("post_action_flag_types") do
+      flags = PostActionType.ordered.where(name_key: ['inappropriate', 'spam', 'notify_moderators'])
+      ActiveModel::ArraySerializer.new(flags, each_serializer: TopicFlagTypeSerializer).as_json
+    end
+
+  end
+
   def default_archetype
     Archetype.default
   end