gt; 2;</PRE
><P>
   </P
><P
>    It turns out that the planner will collapse this tree into a
    two-level query tree: the bottommost <TT
CLASS="COMMAND"
>SELECT</TT
>
    commands will be <SPAN
CLASS="QUOTE"
>"pulled up"</SPAN
> into the middle
    <TT
CLASS="COMMAND"
>SELECT</TT
> since there's no need to process them
    separately.  But the middle <TT
CLASS="COMMAND"
>SELECT</TT
> will remain
    separate from the top, because it contains aggregate functions.
    If we pulled those up it would change t