Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> 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.
Unfortunately I can't read that message right now because archives
isn't responding, but this seems like a pretty bad idea to me.
You still have to do the vacuum cleanup pass (at least in the btree
case, and the only reason gist doesn't need it is it's not yet up
to speed) so there's no real savings.
regards, tom lane