class ActiveRecord::ConnectionAdapters::ReferenceDefinition

def index_options(table_name)
  index_options = as_options(index).merge(conditional_options)
  # legacy reference index names are used on versions 6.0 and earlier
  return index_options if options[:_uses_legacy_reference_index_name]
  index_options[:name] ||= polymorphic_index_name(table_name) if polymorphic
  index_options
end