 can do on our
    views, so we take this opportunity to explain the basics of view
    rules.  The <TT
CLASS="LITERAL"
>SELECT * FROM shoelace</TT
> was
    interpreted by the parser and produced the query tree:

</P><PRE
CLASS="PROGRAMLISTING"
>SELECT shoelace.sl_name, shoelace.sl_avail,
       shoelace.sl_color, shoelace.sl_len,
       shoelace.sl_unit, shoelace.sl_len_cm
  FROM shoelace shoelace;</PRE
><P>

    and this is given to the rule system. The rule system walks through the
    range table and c