Fix UserTrackingConcern firing on every request, optimize some queries (#5368)

- For some reason, :if option on before_action did not work. It got
  executed every time, returned false, and the action run anyway,
  which led to the current_sign_in_at and sign_in_count being
  updated on every request
- Return "do not filter" early in FeedManager#filter_from_home? if
  the status is authored by receiver. Usually this method is not
  called for own statuses at all, but it is called when Feed#get
  uses the database
- Return early if #reload_stale_associations! has nothing to load
  to save a database query with WHERE 1=0

app/controllers/concerns/user_tracking_concern.rb

@@ -7,12 +7,14 @@ module UserTrackingConcern
   UPDATE_SIGN_IN_HOURS = 24
 
   included do
-    before_action :set_user_activity, if: %i(user_signed_in? user_needs_sign_in_update?)
+    before_action :set_user_activity
   end
 
   private
 
   def set_user_activity
+    return unless user_needs_sign_in_update?
+
     # Mark as signed-in today
     current_user.update_tracked_fields!(request)
 
@@ -21,7 +23,7 @@ module UserTrackingConcern
   end
 
   def user_needs_sign_in_update?
-    current_user.current_sign_in_at.nil? || current_user.current_sign_in_at < UPDATE_SIGN_IN_HOURS.hours.ago
+    user_signed_in? && (current_user.current_sign_in_at.nil? || current_user.current_sign_in_at < UPDATE_SIGN_IN_HOURS.hours.ago)
   end
 
   def user_needs_feed_update?

app/lib/feed_manager.rb

@@ -115,6 +115,7 @@ class FeedManager
   end
 
   def filter_from_home?(status, receiver_id)
+    return false if receiver_id == status.account_id
     return true  if status.reply? && (status.in_reply_to_id.nil? || status.in_reply_to_account_id.nil?)
 
     check_for_mutes = [status.account_id]

app/models/notification.rb

@@ -68,6 +68,9 @@ class Notification < ApplicationRecord
   class << self
     def reload_stale_associations!(cached_items)
       account_ids = cached_items.map(&:from_account_id).uniq
+
+      return if account_ids.empty?
+
       accounts = Account.where(id: account_ids).map { |a| [a.id, a] }.to_h
 
       cached_items.each do |item|

app/models/status.rb

@@ -194,7 +194,11 @@ class Status < ApplicationRecord
         account_ids << item.reblog.account_id if item.reblog?
       end
 
-      accounts = Account.where(id: account_ids.uniq).map { |a| [a.id, a] }.to_h
+      account_ids.uniq!
+
+      return if account_ids.empty?
+
+      accounts = Account.where(id: account_ids).map { |a| [a.id, a] }.to_h
 
       cached_items.each do |item|
         item.account = accounts[item.account_id]