Peter Eisentraut <peter_e@gmx.net> writes:
> I have never figured out what the FSM numbers printed by VACUUM VERBOSE really
> meant. I have for example,
> INFO: free space map: 101 relations, 150 pages stored; 1664 total pages
> needed
> What exactly does that last number mean? I have 20000 pages configured for
> the FSM, so if it needs 1664, why does it only take 150?
The FSM allocations are quantized (16 pages per chunk IIRC). So to
store one page for each of 101 relations you'd need 1616 page slots.
It looks like you have three more chunks than the minimum, so some
of those relations have more than 16 pages with free space, but not
very many ...
regards, tom lane