instance method unquote_mariadb_default

# File activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb, line 1098
        def unquote_mariadb_default(field)
          default = field["Default"]
          return if default.nil?

          if default == "NULL"
            # A column declared DEFAULT NULL, which has no default at all.
            field["Default"] = nil
          elsif !default.start_with?("'")
            # An expression rather than a value. A bare `(1 + 1)` is left alone,
            # which is what reading the table directly reports too.
            if /[a-zA-Z_]\w*\(/.match?(default) && !/\ACURRENT_TIMESTAMP/i.match?(default)
              field["Extra"] = "DEFAULT_GENERATED"
            end
          elsif !/\A(?:tiny|medium|long)?(?:text|blob)\b/.match?(field["Type"])
            # Text and blob defaults stay quoted; #new_column_from_field unquotes those.
            field["Default"] = default[1...-1].gsub("''", "'")
              .gsub(/\\(.)/) { MARIADB_DEFAULT_ESCAPES.fetch($1, "\\#{$1}") }
          end
        end