Fix slow distinct queries where grouped queries are faster (#15287)

About 2x speed-up on inboxes query

app/controllers/accounts_controller.rb

@@ -81,7 +81,7 @@ class AccountsController < ApplicationController
   end
 
   def account_media_status_ids
-    @account.media_attachments.attached.reorder(nil).select(:status_id).distinct
+    @account.media_attachments.attached.reorder(nil).select(:status_id).group(:status_id)
   end
 
   def no_replies_scope

app/controllers/admin/statuses_controller.rb

@@ -14,7 +14,7 @@ module Admin
       @statuses = @account.statuses.where(visibility: [:public, :unlisted])
 
       if params[:media]
-        account_media_status_ids = @account.media_attachments.attached.reorder(nil).select(:status_id).distinct
+        account_media_status_ids = @account.media_attachments.attached.reorder(nil).select(:status_id).group(:status_id)
         @statuses.merge!(Status.where(id: account_media_status_ids))
       end
 

app/models/account.rb

@@ -443,7 +443,7 @@ class Account < ApplicationRecord
     end
 
     def inboxes
-      urls = reorder(nil).where(protocol: :activitypub).pluck(Arel.sql("distinct coalesce(nullif(accounts.shared_inbox_url, ''), accounts.inbox_url)"))
+      urls = reorder(nil).where(protocol: :activitypub).group(:preferred_inbox_url).pluck(Arel.sql("coalesce(nullif(accounts.shared_inbox_url, ''), accounts.inbox_url) AS preferred_inbox_url"))
       DeliveryFailureTracker.without_unavailable(urls)
     end
 

app/models/form/account_batch.rb

@@ -51,7 +51,7 @@ class Form::AccountBatch
   end
 
   def account_domains
-    accounts.pluck(Arel.sql('distinct domain')).compact
+    accounts.group(:domain).pluck(:domain).compact
   end
 
   def accounts