On Thursday, April 23rd, 2026 at 3:10 PM, David Rowley <dgrowleyml@gmail.com> wrote:

> On Fri, 24 Apr 2026 at 01:04, Mok <gurmokh@protonmail.com> wrote:
> >
> > On Thursday, April 23rd, 2026 at 4:44 AM, David Rowley <dgrowleyml@gmail.com> wrote:
> >
> > > On Thu, 23 Apr 2026 at 08:19, Mok <gurmokh@protonmail.com> wrote:
> > > > For example, set to 0.8 a 'standard' vacuum would be triggered when the table reached 160million with a default 200million setting.
> > >
> > > If that's what you want, why wouldn't you set the
> > > autovacuum_freeze_max_age to 160million?
> >
> > Because that would trigger a 'to-prevent-wraparound' vacuum, which is what this change is trying to avoid.
>
> Yes, it would. Why do you want to prevent them? I believe a few people
> have been alarmed in the past about the "to prevent wraparound" text
> in pg_stat_activity or when they saw those words in the logs. The
> default 200 million autovacuum_freeze_max_age setting triggers an
> autovacuum when it's less than 10% of the way into exhausting the
> transaction space for the table. What you're proposing with an
> autovacuum_age_scale_factor of 0.1 sounds like it would result in an
> auto-vacuum when only 1% of the transaction ID space is consumed! I
> think you're under the false impression that these anti-wraparound
> vacuums are bad. They're not.
>
> There's some documentation that might be worthwhile reading in [1].
>
> David
>
> [1] https://www.postgresql.org/docs/18/routine-vacuuming.html#VACUUM-FOR-WRAPAROUND
>

> On large tables they can be quite inconvenient so avoiding them is preferable. My example of 0.1 is to test the patch if you tried it. The range for this 

> setting is 0.1 -> 1 with the latter effectively rendering the setting moot.

I don't know where you got that idea from. For example have a table with 1 billion records, autovacuum_vacuum_scale_factor = 0.01 , 

50+1000000000 *0.01 = 10000050 ,you can reduce autovacuum_vacuum_max_threshold  substantially lower than 10000050 ，

vacthresh = (float4) vac_base_thresh + vac_scale_factor * reltuples;

if (vac_max_thresh >= 0 && vacthresh > (float4) vac_max_thresh)

vacthresh = (float4) vac_max_thresh;

There's no fundamental difference between this and your parameter