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" <pgsql-hackers@postgresql.org>, Shruthi Gowda <gowdashru@gmail.com>
Date: 2022-08-02T19:44:40Z
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 8/2/22 3:39 PM, Tom Lane wrote:
> "Jonathan S. Katz" <jkatz@postgresql.org> writes:
>> On 8/2/22 3:23 PM, Robert Haas wrote:
>>> I'm not quite sure how to rule that theory in or out, though.
> 
>> Without overcomplicating this, are we able to check to see if autovacuum
>> ran during the course of the test?
> 
> Looks like we're all thinking along the same lines.
> 
> While not smoking guns, these definitely prove that autovac was active.

 > If that is the explanation, then it leaves us with few good options.
 > I am not in favor of disabling autovacuum in the test: ordinary
 > users are not going to do that while pg_upgrade'ing, so it'd make
 > the test less representative of real-world usage, which seems like
 > a bad idea.  We could either drop this particular check again, or
 > weaken it to allow new relfrozenxid >= old relfrozenxid, likewise
 > relminxid.

The test does look helpful and it would catch regressions. Loosely 
quoting Robert on a different point upthread, we don't want to turn off 
the alarm just because it's spuriously going off.

I think the weakened check is OK (and possibly mimics the real-world 
where autovacuum runs), unless you see a major drawback to it?

Jonathan