   a different default expression than its parent column.  If the default
      is textually identical to the parent's default, but not actually the
      same (for instance, because of schema search path differences) it would
      not be recognized as different, so that after dump and restore the
      child would be allowed to inherit the parent's default.  Child columns
      that are <TT
CLASS="LITERAL"
>NOT NULL</TT
> where their parent is not could also be
      restored subtly incorrectly.
     </P
