BUG #5322: Time to perform vacuums

The following bug has been logged online:

Bug reference:      5322
Logged by:          Eric Pailleau
Email address:      eric@numlog.fr
PostgreSQL version: 8.2.3
Operating system:   linux debian
Description:        Time to perform vacuums
Details:

Hello,
I really don't know if it can be a bug or not,
but when I do a 'VACCUM FULL ANALYZE VERBOSE',
it can take a very long time (expecially on large tables), while doing this
sequence of 3 commands is
quite quicker (on my system at least).

VACCUM VERBOSE
then
VACCUM FULL VERBOSE
then
VACCUM FULL ANALYZE VERBOSE

I mean adding the 'three commands' times is less than the time for the
direct 'VACCUM FULL ANALYZE VERBOSE'.

Does the fact of doing a 'simple' VACUUM first, make
other VACCUM more quick ? Does it finally does the same ? Is it only
coincidence due to system load ?

Thanks for your comments about this...