"Jeffrey W. Baker" <jwbaker@acm.org> writes:
> I shut down all connections, and vacuum has a different output:
> NOTICE: Pages 33639: Changed 226, Empty 0; Tup 128819: Vac 2840812,
> Keep 0, UnUsed 96275.
> Total CPU 14.29s/28.69u sec elapsed 233.02 sec.
Ah-hah, you did have open transactions.
> So I conclude from these two data points that Keep means tuples that are
> still visible to a transaction, Vac means tuples that are not visible to
> any transaction. But, what is UnUsed?
Looking at the code:
Tup # tuples remaining after vacuum
Vac # tuples removed by vacuum
Keep # dead tuples kept because some xact can still see 'em
Unused # unused item pointers
"Keep" is included in the "Tup" total.
The unused item pointers may get recycled later; it looks like that
hasn't been determined yet at the point where these stats are printed.
regards, tom lane