Updated FSM display for VACUUM VERBOSE

I have trouble understanding the current output of VACUUM VERBOSE when
it displays FSM information.

The current output is:

INFO: free space map: 49 relations, 17266 pages stored; 18768 total
pages used
DETAIL: FSM size: 1000 relations + 18000 pages = 171 kB shared memory.
NOTICE: the number of page slots needed (18768) exceeds max_fsm_pages
(18000)
HINT: Consider increasing the configuration parameter "max_fsm_relations"
to a value over 18768.

The problem I have is that the relations part is mixed with the pages
part, and the numbers aren't easily comparable. I have attached a patch
which makes the information easier to understand. Here is one where the
FSM is large enough:

INFO: free space map: 48 relations with free space, maximum of 1000 relations trackable
INFO: 35 pages stored, 768 pages used (with overhead)
INFO: 768 pages required to store all freespace, maximum of 18000 pages allocatable (171 kB)

and one that is too small:

INFO: free space map: 49 relations with free space, maximum of 1000 relations trackable
INFO: 17266 pages stored, 18000 pages used (with overhead)
INFO: 18768 pages required to store all freespace, maximum of 18000 pages allocatable (171 kB)
NOTICE: the number of page slots needed (18768) exceeds max_fsm_pages (18000)
HINT: Consider increasing the configuration parameter "max_fsm_relations"
to a value over 18768.

I find this output cleaner and easier to understand. The "pages used"
value will match either the "required" or "maximum" value on the line
below.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073