Horton

Re: pg15b2: large objects lost on upgrade

Jonathan S. Katz <jkatz@postgresql.org>

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From: "Jonathan S. Katz" <jkatz@postgresql.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Robert Haas <robertmhaas@gmail.com>, Noah Misch <noah@leadboat.com>, Andrew Dunstan <andrew@dunslane.net>, Bruce Momjian <bruce@momjian.us>, Michael Paquier <michael@paquier.xyz>, Justin Pryzby <pryzby@telsasoft.com>, pgsql-hackers@postgresql.org, Shruthi Gowda <gowdashru@gmail.com>
Date: 2022-08-03T14:53:06Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Revert recent changes to 002_pg_upgrade.pl.

  2. Revise test case added in 43746996399541ecb5c7b188725a5f097c15ceae.

  3. Use TRUNCATE to preserve relfilenode for pg_largeobject + index.

  4. Preserve relfilenode of pg_largeobject and its index across pg_upgrade.

  5. Have VACUUM warn on relfrozenxid "in the future".

  6. Set relfrozenxid to oldest extant XID seen by VACUUM.

  7. pg_upgrade: Preserve relfilenodes and tablespace OIDs.

  8. Perform a lot more sanity checks when freezing tuples.

> On Aug 3, 2022, at 10:14 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> 
> Robert Haas <robertmhaas@gmail.com> writes:
>>> On Tue, Aug 2, 2022 at 3:51 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>> I also think that ">=" is a sufficient requirement.
> 
>> I don't really like this approach. Imagine that the code got broken in
>> such a way that relfrozenxid and relminmxid were set to a value chosen
>> at random - say, the contents of 4 bytes of unallocated memory that
>> contained random garbage. Well, right now, the chances that this would
>> cause a test failure are nearly 100%. With this change, they'd be
>> nearly 0%.
> 
> If you have a different solution that you can implement by, say,
> tomorrow, then go for it.  But I want to see some fix in there
> within about 24 hours, because 15beta3 wraps on Monday and we
> will need at least a few days to see if the buildfarm is actually
> stable with whatever solution is applied.

Yeah, I would argue that the current proposal
guards against the false positives as they currently stand.

I do think Robert raises a fair point, but I wonder
if another test would catch that? I don’t want to
say “this would never happen” because, well,
it could happen. But AIUI this would probably
manifest itself in other places too?

> A possible compromise is to allow new values that are between
> old value and old-value-plus-a-few-dozen.

Well, that’s kind of deterministic :-) I’m OK
with that tweak, where “OK” means not thrilled,
but I don’t see a better way to get more granular
details (at least through my phone searches).

I can probably have a tweak for this in a couple
of hours if and when I’m on plane wifi.

Jonathan