Introduce ApplicationController#cache_collection_paginated_by_id (#14677)

* Replace incorrect use of distinct with group

Some uses of ActiveRecord::QueryMethods#distinct pass field names but they
are incorrect for the current version of Rails.

ActiveRecord::QueryMethods#group provides the expected behavior and
benefits performance. See commit 6da24aad4cafdef8d8a2c92bac2002a5fc2fe9c8.

* Introduce ApplicationController#cache_collection_paginated_by_id

ApplicationController#cache_collection_paginated_by_id fuses
ApplicationController#cache_collection and Paginable.paginate_by_id.

An advantage of this method is that it prevents from modifying scope which
Paginable.paginate_by_id may provide.
ApplicationController#cache_collection always return an array and there
is no possibility of the scope modification. It is also clear for a
programmer, considering the implication of "cache".

This method can also emit more efficient queries by using
Cacheable.cache_ids before calling Paginable.paginate_by_id.

app/controllers/api/v1/timelines/public_controller.rb

@@ -16,18 +16,20 @@ class Api::V1::Timelines::PublicController < Api::BaseController
   end
 
   def load_statuses
-    cached_public_statuses
+    cached_public_statuses_page
   end
 
-  def cached_public_statuses
-    cache_collection public_statuses, Status
-  end
-
-  def public_statuses
-    statuses = public_timeline_statuses.paginate_by_id(
+  def cached_public_statuses_page
+    cache_collection_paginated_by_id(
+      public_statuses,
+      Status,
       limit_param(DEFAULT_STATUSES_LIMIT),
       params_slice(:max_id, :since_id, :min_id)
     )
+  end
+
+  def public_statuses
+    statuses = public_timeline_statuses
 
     if truthy_param?(:only_media)
       statuses.joins(:media_attachments).group(:id)

app/controllers/api/v1/timelines/tag_controller.rb

@@ -20,23 +20,18 @@ class Api::V1::Timelines::TagController < Api::BaseController
   end
 
   def cached_tagged_statuses
-    cache_collection tagged_statuses, Status
-  end
-
-  def tagged_statuses
     if @tag.nil?
       []
     else
-      statuses = tag_timeline_statuses.paginate_by_id(
+      statuses = tag_timeline_statuses
+      statuses = statuses.joins(:media_attachments) if truthy_param?(:only_media)
+
+      cache_collection_paginated_by_id(
+        statuses,
+        Status,
         limit_param(DEFAULT_STATUSES_LIMIT),
         params_slice(:max_id, :since_id, :min_id)
       )
-
-      if truthy_param?(:only_media)
-        statuses.joins(:media_attachments)
-      else
-        statuses
-      end
     end
   end