Re: another autovacuum scheduling thread

HI Nathan

> That approach would begin aggressively scaling the priority of tables
> sooner, but I don't know if that's strictly better.  In any case, I'd like
> to avoid making the score calculation too magical.
In fact, with the introduction of the vacuum_max_eager_freeze_failure_rate
feature, if a table’s age still exceeds more than 1.x times the
autovacuum_freeze_max_age, it suggests that the vacuum freeze process is
not functioning properly. Once the age surpasses vacuum_failsafe_age,
wraparound issues are likely to occur soon.Taking the average of
vacuum_failsafe_age and autovacuum_freeze_max_age is not a complex
approach. Under the default configuration, this average already exceeds
four times the autovacuum_freeze_max_age. At that stage, a DBA should have
already intervened to investigate and resolve why the table age is not
decreasing.

Thanks

On Thu, Oct 30, 2025 at 12:07 AM Nathan Bossart <nathandbossart@gmail.com>
wrote:

> On Wed, Oct 29, 2025 at 10:24:17AM -0500, Sami Imseih wrote:
> > I think we do need some documentation about this behavior, which v6 is
> > still missing.
>
> Would you be interested in giving that part a try?
>
> > Another thing I have been contemplating about is the change in
> prioritization
> > and the resulting difference in the order in which tables are vacuumed
> > is what it means for workloads in which autovacuum tuning that was
> > done with the current assumptions will no longer be beneficial.
> >
> > Let's imagine staging tables that get created and dropped during
> > some batch processing window and they see huge data
> > ingestion/changes. The current scan will make these less of a priority
> > naturally in relation to other permanent tables, but with the new
> priority,
> > we are making these staging tables more of a priority. Users will now
> > need to maybe turn off autovacuum on a per-table level to prevent this
> > scenario. That is just one example.
> >
> > What I am also trying to say is should we provide a way, I hate
> > to say a GUC, for users to go back to the old behavior? or am I
> > overstating the risk here?
>
> It's probably worth testing out this scenario, but I can't say I'm terribly
> worried.  Those kinds of tables are already getting chosen by autovacuum
> earlier due to reltuples == -1, and this patch will just move them to the
> front of the list that autovacuum creates.  In any case, I'd really like to
> avoid a GUC or fallback switch here.
>
> --
> nathan
>
>
>