We discussed an optimization of VACUUM here
http://archives.postgresql.org/pgsql-hackers/2005-09/msg00046.php
that would allow VACUUM to complete faster by avoiding scanning the
indexes when no rows were removed from the heap by the VACUUM.
Patch applies cleanly on cvstip; make check passes.
Tests shows clear performance gain when no rows removed by VACUUM.
Not as useful as may once have been, but certainly no loss either,
whatever happens in the future with VACUUM.
Best Regards, Simon Riggs