Re: pg15b2: large objects lost on upgrade

Peter Geoghegan <pg@bowt.ie>

From: Peter Geoghegan <pg@bowt.ie>

To: Andres Freund <andres@anarazel.de>

Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, "Jonathan S. Katz" <jkatz@postgresql.org>, 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" <pgsql-hackers@postgresql.org>, Shruthi Gowda <gowdashru@gmail.com>

Date: 2022-08-03T20:29:25Z

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 →

Revert recent changes to 002_pg_upgrade.pl.
- 6f7e7d0c482d 15.0 landed
- 87e22f675fd8 16.0 landed
Revise test case added in 43746996399541ecb5c7b188725a5f097c15ceae.
- d92f2bc0dae3 15.0 landed
- 212bdc0cbc32 16.0 landed
Use TRUNCATE to preserve relfilenode for pg_largeobject + index.
- bbe08b8869bd 16.0 landed
- 4ab5dae9472c 15.0 landed
Preserve relfilenode of pg_largeobject and its index across pg_upgrade.
- a2996478c32d 15.0 landed
- d498e052b4b8 16.0 landed
Have VACUUM warn on relfrozenxid "in the future".
- e83ebfe6d767 15.0 cited
Set relfrozenxid to oldest extant XID seen by VACUUM.
- 0b018fabaaba 15.0 cited
pg_upgrade: Preserve relfilenodes and tablespace OIDs.
- 9a974cbcba00 15.0 cited
Perform a lot more sanity checks when freezing tuples.
- 699bf7d05c68 11.0 cited

On Wed, Aug 3, 2022 at 1:20 PM Andres Freund <andres@anarazel.de> wrote:
> > 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%.
>
> Can't that pretty easily be addressed by subsequently querying txid_current(),
> and checking that the value isn't newer than that?

It couldn't hurt to do that as well, in passing (at the same time as
testing that newrelfrozenxid >= oldrelfrozenxid directly). But
deliberately running VACUUM afterwards seems like a good idea. We
really ought to expect VACUUM to catch cases where
relfrozenxid/relminmxid is faulty, at least in cases where it can be
proven wrong by noticing some kind of inconsistency.

-- 
Peter Geoghegan