1 files changed, 18 insertions, 0 deletions
diff --git a/app/models/application_setting.rb b/app/models/application_setting.rb
index 661b10019ad..eb46be65858 100644
--- a/app/models/application_setting.rb
+++ b/app/models/application_setting.rb
@@ -426,6 +426,8 @@ class ApplicationSetting < ApplicationRecord
   end
 
   def self.create_from_defaults
+    check_schema!
+
     transaction(requires_new: true) do
       super
     end
@@ -434,6 +436,22 @@ class ApplicationSetting < ApplicationRecord
     current_without_cache
   end
 
+  # Due to the frequency with which settings are accessed, it is
+  # likely that during a backup restore a running GitLab process
+  # will insert a new `application_settings` row before the
+  # constraints have been added to the table. This would add an
+  # extra row with ID 1 and prevent the primary key constraint from
+  # being added, which made ActiveRecord throw a
+  # IrreversibleOrderError anytime the settings were accessed
+  # (https://gitlab.com/gitlab-org/gitlab/-/issues/36405).  To
+  # prevent this from happening, we do a sanity check that the
+  # primary key constraint is present before inserting a new entry.
+  def self.check_schema!
+    return if ActiveRecord::Base.connection.primary_key(self.table_name).present?
+
+    raise "The `#{self.table_name}` table is missing a primary key constraint in the database schema"
+  end
+
   # By default, the backend is Rails.cache, which uses
   # ActiveSupport::Cache::RedisStore. Since loading ApplicationSetting
   # can cause a significant amount of load on Redis, let's cache it in