Re: pg14b2: FailedAssertion("_bt_posting_valid(nposting)", File: "nbtdedup.c", ...

On Sun, Jun 27, 2021 at 6:47 PM Justin Pryzby <pryzby@telsasoft.com> wrote:
> I've just realized that this VM has a strange storage configuration.
>
> It's using LVM thin pools, which I don't use anywhere else.
> Someone else set this up, and I think I've literally never used pools before.
> Some time ago, the pool ran out of space, and I ran LVM repair on it.
> It seems very possible that's the issue.
> A latent problem might've been tickled by pg_upgrade --link.

Anything is possible, of course, but even if this is a bug in Postgres
it isn't particularly likely to be a bug in the nbtree code. We see
clear signs of general corruption here, which is apparently not
limited to the one page that you supplied to me privately -- since
AFAICT that's not the page that amcheck throws the error on.

> That said, the relevant table is the active "alarms" table, and it would've
> gotten plenty of DML with no issue for months running v13.

It might not have been visibly broken without assertions enabled,
though. I sprinkled nbtdedup.c with these _bt_posting_valid()
assertions just because it was easy. The assertions were bound to
catch some problem sooner or later, and had acceptable overhead.

-- 
Peter Geoghegan