instance method load_schema!

# File activerecord/lib/active_record/model_schema.rb, line 588
        def load_schema!
          unless table_name
            raise ActiveRecord::TableNotSpecified, "#{self} has no table configured. Set one with #{self}.table_name="
          end

          columns_hash = schema_cache.columns_hash(table_name)
          columns_hash = columns_hash.except(*ignored_columns) unless ignored_columns.empty?
          @columns_hash = columns_hash.freeze

          _default_attributes # Precompute to cache DB-dependent attribute types
        end