Re: pgsql: Add per-index stats information in verbose logs of autovacuum

On Mon, Mar 22, 2021 at 9:28 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> Add per-index stats information in verbose logs of autovacuum

I think that this is very helpful -- thanks for working on it.
However, it seems to me that "%u remain" is misleading. I am referring
to this line of output:

index "dups_idx": pages: 1431 remain, 1343 newly deleted, 1427
currently deleted, 84 reusable

It suggests that the index file can shrink. As if the remaining pages
are left now that the pages we deleted have been returned to the OS. I
think that this same line of output should look like this instead:

index "dups_idx": 1431 pages in total, 1343 newly deleted,
1427 currently deleted, 84 reusable

FWIW this is roughly the corresponding point of equivalent VACUUM
VERBOSE output:

INFO: index "dups_idx" now contains 0 row versions in 1431 pages

To be clear, I agree that it would not be sensible to make the
log_autovacuum_min_duration output 100% consistent with VACUUM
VERBOSE. I just think that "%u remain" is misleading. It's just that
one detail.

--
Peter Geoghegan