Re: Count and log pages set all-frozen by vacuum

On Tue, Nov 26, 2024 at 8:38 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > visibility map: 5 pages set all-visible, 4 pages set all-frozen.
>
> Which means that 5 pages were marked as only all-visible and 4 pages
> were marked as all-frozen (and possibly all-visible too). The total
> number of pages' whose VM status changed is the sum of these two
> numbers, 9 pages. We would have no idea how many total VM bits were
> set, though.

To me, the above output means 9 bits changed, 5 of which were
all-visible bits and 4 of which were all-frozen bits. It doesn't say
whether they were the same pages or not (although we might be able to
infer that based on only 3 of the 4 states being valid).

If you want to count the number of pages that changed state, then I
think the message wording needs to be different, but personally I
think counting the number of flipped bits of each type seems easier to
understand.

--
Robert Haas
EDB: http://www.enterprisedb.com