Improve counter caches on Status and Account (#7644)

Do not touch statuses_count on accounts table when mass-destroying
statuses to reduce load when removing accounts, same for
reblogs_count and favourites_count

Do not count statuses with direct visibility in statuses_count

Fix #828

app/models/status.rb

@@ -41,12 +41,12 @@ class Status < ApplicationRecord
 
   belongs_to :application, class_name: 'Doorkeeper::Application', optional: true
 
-  belongs_to :account, inverse_of: :statuses, counter_cache: true
+  belongs_to :account, inverse_of: :statuses
   belongs_to :in_reply_to_account, foreign_key: 'in_reply_to_account_id', class_name: 'Account', optional: true
   belongs_to :conversation, optional: true
 
   belongs_to :thread, foreign_key: 'in_reply_to_id', class_name: 'Status', inverse_of: :replies, optional: true
-  belongs_to :reblog, foreign_key: 'reblog_of_id', class_name: 'Status', inverse_of: :reblogs, counter_cache: :reblogs_count, optional: true
+  belongs_to :reblog, foreign_key: 'reblog_of_id', class_name: 'Status', inverse_of: :reblogs, optional: true
 
   has_many :favourites, inverse_of: :status, dependent: :destroy
   has_many :reblogs, foreign_key: 'reblog_of_id', class_name: 'Status', inverse_of: :reblog, dependent: :destroy
@@ -167,6 +167,17 @@ class Status < ApplicationRecord
     @emojis ||= CustomEmoji.from_text([spoiler_text, text].join(' '), account.domain)
   end
 
+  def mark_for_mass_destruction!
+    @marked_for_mass_destruction = true
+  end
+
+  def marked_for_mass_destruction?
+    @marked_for_mass_destruction
+  end
+
+  after_create  :increment_counter_caches
+  after_destroy :decrement_counter_caches
+
   after_create_commit :store_uri, if: :local?
   after_create_commit :update_statistics, if: :local?
 
@@ -388,4 +399,40 @@ class Status < ApplicationRecord
     return unless public_visibility? || unlisted_visibility?
     ActivityTracker.increment('activity:statuses:local')
   end
+
+  def increment_counter_caches
+    return if direct_visibility?
+
+    if association(:account).loaded?
+      account.update_attribute(:statuses_count, account.statuses_count + 1)
+    else
+      Account.where(id: account_id).update_all('statuses_count = COALESCE(statuses_count, 0) + 1')
+    end
+
+    return unless reblog?
+
+    if association(:reblog).loaded?
+      reblog.update_attribute(:reblogs_count, reblog.reblogs_count + 1)
+    else
+      Status.where(id: reblog_of_id).update_all('reblogs_count = COALESCE(reblogs_count, 0) + 1')
+    end
+  end
+
+  def decrement_counter_caches
+    return if direct_visibility? || marked_for_mass_destruction?
+
+    if association(:account).loaded?
+      account.update_attribute(:statuses_count, [account.statuses_count - 1, 0].max)
+    else
+      Account.where(id: account_id).update_all('statuses_count = GREATEST(COALESCE(statuses_count, 0) - 1, 0)')
+    end
+
+    return unless reblog?
+
+    if association(:reblog).loaded?
+      reblog.update_attribute(:reblogs_count, [reblog.reblogs_count - 1, 0].max)
+    else
+      Status.where(id: reblog_of_id).update_all('reblogs_count = GREATEST(COALESCE(reblogs_count, 0) - 1, 0)')
+    end
+  end
 end