From: | Noah Misch <noah(at)leadboat(dot)com> |
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To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
Subject: | Re: What is "wraparound failure", really? |
Date: | 2021-06-30 03:07:27 |
Message-ID: | 20210630030727.GD2062625@rfd.leadboat.com |
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Lists: | pgsql-hackers |
On Mon, Jun 28, 2021 at 08:51:50AM -0400, Andrew Dunstan wrote:
> On 6/28/21 2:39 AM, Peter Geoghegan wrote:
> > I agree that in practice that's often fine. But my point is that there
> > is another very good reason to not increase autovacuum_freeze_max_age,
> > contrary to what the docs say (actually there is a far better reason
> > than truncating clog). Namely, increasing it will generally increase
> > the risk of VACUUM not finishing in time.
Yep, that doc section's priorities are out of date.
> But if you're really worried about people setting
> autovacuum_freeze_max_age too high, then maybe we should be talking
> about capping it at a lower level rather than adjusting the docs that
> most users don't read.
If a GUC minimum or maximum feels like a mainstream choice, it's probably too
strict. Hence, I think the current maximum is fine. At 93% of the XID space,
it's not risk-averse, but it's not absurd.
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