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 ，
