On Thu, 29 Jan 2026 at 10:00, Alexander Lakhin <[email protected]> wrote:
>
> Hello Melanie,
>
> 29.01.2026 01:16, Melanie Plageman wrote:
>
> Thanks for the review!
> I pushed v33 0001-0003 after incorporating your feedback.
>
>
> The buildfarm animal scorpion has detected an instability of the addition
> to pg_visibility from 21796c267 [1]:
>
> 80/82 postgresql:pg_visibility-running / pg_visibility-running/regress
> ERROR 7.23s exit status 1
>
> diff -U3
> /home/bf/bf-build/scorpion/HEAD/pgsql/contrib/pg_visibility/expected/pg_visibility.out
>
> /home/bf/bf-build/scorpion/HEAD/pgsql.build/testrun/pg_visibility-running/regress/results/pg_visibility.out
> ---
> /home/bf/bf-build/scorpion/HEAD/pgsql/contrib/pg_visibility/expected/pg_visibility.out
> 2026-01-26 22:07:12.923378464 +0100
> +++
> /home/bf/bf-build/scorpion/HEAD/pgsql.build/testrun/pg_visibility-running/regress/results/pg_visibility.out
> 2026-01-28 20:15:13.802517085 +0100
> @@ -213,7 +213,7 @@
> select pg_visibility_map_summary('test_vac_unmodified_heap');
> pg_visibility_map_summary
> ---------------------------
> - (1,1)
> + (0,0)
> (1 row)
>
> -- the checkpoint cleans the buffer dirtied by freezing the sole tuple
> @@ -237,7 +237,7 @@
> FROM page_header(get_raw_page('test_vac_unmodified_heap', 0));
> ?column?
> ----------
> - t
> + f
> (1 row)
>
> -- vacuum sets the VM
>
> I've managed to reproduce it locally with the attached and:
> echo "autovacuum_naptime = 1" > /tmp/temp.config
> TEMP_CONFIG=/tmp/temp.config make -s check -C contrib/pg_visibility/
> ...
> ok 85 - pg_visibility 30 ms
> not ok 86 - pg_visibility 165 ms
> ok 87 - pg_visibility 36 ms
> ...
> # 1 of 100 tests failed.
>
> Could you please look at this?
>
> Probably you'll find [2] helpful.
>
> [1]
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=scorpion&dt=2026-01-28%2019%3A07%3A32
> [2] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=1c64d2fcb
>
> Best regards,
> Alexander
Thanks Alexander!
This is a good and detailed report, I was able to reproduce this.
I have added some logs to my copy of postgres with your patch and I
think problem causing this test to fail is this sequence:
1) Autovacuum starts, does its deeds, and acquiring xid = 118518
2) insert into test_vac_unmodified_heap values (1); executes and
commits with xid = 118519 (from my log)
3) vacuum freeze starts and computes cutoff xid = 118518, because
oldest xmin is 118518 from (1)
*and we cannot freeze tuple*
```
2026-01-29 13:27:44.559 UTC [133670] DEBUG: CommitTransaction(1)
name: unnamed; blockState: STARTED; state: INPROGRESS, xid/subid/cid:
118519/1/0 (used)
...
2026-01-29 13:27:44.559 UTC [133672] DEBUG: CommitTransaction(1)
name: unnamed; blockState: STARTED; state: INPROGRESS, xid/subid/cid:
118518/1/2
...
2026-01-29 13:27:44.560 UTC [133670] INFO: finished vacuuming
"contrib_regression.public.test_vac_unmodified_heap": index scans: 0
pages: 0 removed, 1 remain, 1 scanned (100.00% of total), 0
eagerly scanned
tuples: 0 removed, 1 remain, 0 are dead but not yet removable
removable cutoff: 118518, which was 2 XIDs old when operation ended
new relfrozenxid: 118518, which is 1 XIDs ahead of previous value
frozen: 0 pages from table (0.00% of total) had 0 tuples frozen
visibility map: 0 pages set all-visible, 0 pages set
all-frozen (0 were all-visible)
index scan not needed: 0 pages from table (0.00% of total) had
0 dead item identifiers removed
avg read rate: 0.000 MB/s, avg write rate: 54.253 MB/s
buffer usage: 22 hits, 0 reads, 3 dirtied
```
I did not come up with a fix yet though.
--
Best regards,
Kirill Reshke
