Announcement reactions query spec improvement and refactor (#28768)

app/models/announcement.rb

@@ -75,22 +75,41 @@ class Announcement < ApplicationRecord
   end
 
   def reactions(account = nil)
-    records = begin
-      scope = announcement_reactions.group(:announcement_id, :name, :custom_emoji_id).order(Arel.sql('MIN(created_at) ASC'))
-
-      if account.nil?
-        scope.select('name, custom_emoji_id, count(*) as count, false as me')
-      else
-        scope.select("name, custom_emoji_id, count(*) as count, exists(select 1 from announcement_reactions r where r.account_id = #{account.id} and r.announcement_id = announcement_reactions.announcement_id and r.name = announcement_reactions.name) as me")
+    grouped_ordered_announcement_reactions.select(
+      [:name, :custom_emoji_id, 'COUNT(*) as count'].tap do |values|
+        values << value_for_reaction_me_column(account)
       end
-    end.to_a
-
-    ActiveRecord::Associations::Preloader.new(records: records, associations: :custom_emoji).call
-    records
+    ).to_a.tap do |records|
+      ActiveRecord::Associations::Preloader.new(records: records, associations: :custom_emoji).call
+    end
   end
 
   private
 
+  def grouped_ordered_announcement_reactions
+    announcement_reactions
+      .group(:announcement_id, :name, :custom_emoji_id)
+      .order(
+        Arel.sql('MIN(created_at)').asc
+      )
+  end
+
+  def value_for_reaction_me_column(account)
+    if account.nil?
+      'FALSE AS me'
+    else
+      <<~SQL.squish
+        EXISTS(
+          SELECT 1
+          FROM announcement_reactions inner_reactions
+          WHERE inner_reactions.account_id = #{account.id}
+            AND inner_reactions.announcement_id = announcement_reactions.announcement_id
+            AND inner_reactions.name = announcement_reactions.name
+        ) AS me
+      SQL
+    end
+  end
+
   def set_published
     return unless scheduled_at.blank? || scheduled_at.past?