Fix performance on instances list in admin UI (#15282)

- Reduce duplicate queries
- Remove n+1 queries
- Add accounts count to detailed view
- Add separate action log entry for updating existing domain blocks

app/models/instance.rb

@@ -1,26 +1,63 @@
 # frozen_string_literal: true
+# == Schema Information
+#
+# Table name: instances
+#
+#  domain         :string           primary key
+#  accounts_count :bigint(8)
+#
 
-class Instance
-  include ActiveModel::Model
+class Instance < ApplicationRecord
+  self.primary_key = :domain
 
-  attr_accessor :domain, :accounts_count, :domain_block
+  has_many :accounts, foreign_key: :domain, primary_key: :domain
 
-  def initialize(resource)
-    @domain         = resource.domain
-    @accounts_count = resource.respond_to?(:accounts_count) ? resource.accounts_count : nil
-    @domain_block   = resource.is_a?(DomainBlock) ? resource : DomainBlock.rule_for(domain)
-    @domain_allow   = resource.is_a?(DomainAllow) ? resource : DomainAllow.rule_for(domain)
+  belongs_to :domain_block, foreign_key: :domain, primary_key: :domain
+  belongs_to :domain_allow, foreign_key: :domain, primary_key: :domain
+
+  scope :matches_domain, ->(value) { where(arel_table[:domain].matches("%#{value}%")) }
+
+  def self.refresh
+    Scenic.database.refresh_materialized_view(table_name, concurrently: true, cascade: false)
   end
 
-  def countable?
-    @accounts_count.present?
+  def readonly?
+    true
+  end
+
+  def delivery_failure_tracker
+    @delivery_failure_tracker ||= DeliveryFailureTracker.new(domain)
+  end
+
+  def following_count
+    @following_count ||= Follow.where(account: accounts).count
+  end
+
+  def followers_count
+    @followers_count ||= Follow.where(target_account: accounts).count
+  end
+
+  def reports_count
+    @reports_count ||= Report.where(target_account: accounts).count
+  end
+
+  def blocks_count
+    @blocks_count ||= Block.where(target_account: accounts).count
+  end
+
+  def public_comment
+    domain_block&.public_comment
+  end
+
+  def private_comment
+    domain_block&.private_comment
+  end
+
+  def media_storage
+    @media_storage ||= MediaAttachment.where(account: accounts).sum(:file_file_size)
   end
 
   def to_param
     domain
   end
-
-  def cache_key
-    domain
-  end
 end