Re: New IndexAM API controlling index vacuum strategies

On Thu, Mar 18, 2021 at 12:23 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>
> On Wed, Mar 17, 2021 at 7:16 PM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> > Since I was thinking that always skipping index vacuuming on
> > anti-wraparound autovacuum is legitimate, skipping index vacuuming
> > only when we're really close to the point of going into read-only mode
> > seems a bit conservative, but maybe a good start. I've attached a PoC
> > patch to disable index vacuuming if the table's relfrozenxid is too
> > older than autovacuum_freeze_max_age (older than 1.5x of
> > autovacuum_freeze_max_age).
>
> Most anti-wraparound VACUUMs are really not emergencies, though. So
> treating them as special simply because they're anti-wraparound
> vacuums doesn't seem like the right thing to do. I think that we
> should dynamically decide to do this when (antiwraparound) VACUUM has
> already been running for some time. We need to delay the decision
> until it is almost certainly true that we really have an emergency.

That's a good idea to delay the decision until two_pass_strategy().

>
> Can you take what you have here, and make the decision dynamic? Delay
> it until we're done with the first heap scan? This will require
> rebasing on top of the patch I posted. And then adding a third patch,
> a little like the second patch -- but not too much like it.

Attached the updated patch that can be applied on top of your v3 patches.

Regards,

--
Masahiko Sawada
EDB: https://www.enterprisedb.com/