 is to be deleted (by <TT
CLASS="COMMAND"
>VACUUM</TT
>), all its
       index entries must be removed first.
      </P
></LI
><LI
><P
>       An index scan must maintain a pin
       on the index page holding the item last returned by
       <CODE
CLASS="FUNCTION"
>amgettuple</CODE
>, and <CODE
CLASS="FUNCTION"
>ambulkdelete</CODE
> cannot delete
       entries from pages that are pinned by other backends.  The need
       for this rule is explained below.
      </P
></LI
></UL
><P>

   Without the third r