Re: relfrozenxid may disagree with row XIDs after 1ccc1e05ae

Melanie Plageman <melanieplageman@gmail.com>

From: Melanie Plageman <melanieplageman@gmail.com>

To: Bowen Shi <zxwsbg12138@gmail.com>

Cc: Robert Haas <robertmhaas@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Noah Misch <noah@leadboat.com>, Peter Geoghegan <pg@bowt.ie>, Alexander Lakhin <exclusion@gmail.com>, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>, Andres Freund <andres@anarazel.de>

Date: 2024-05-13T14:42:31Z

Lists: pgsql-bugs

Commits

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

Ensure vacuum removes all visibly dead tuples older than OldestXmin
- 06bf404cd07b 16.4 landed
- 45ce054c02b8 14.13 landed
- dc6354c67017 15.8 landed
Combine freezing and pruning steps in VACUUM
- 6dbb490261a6 17.0 cited
Handle non-chain tuples outside of heap_prune_chain()
- 6f47f6883151 17.0 cited
Fix false reports in pg_visibility
- e85662df44ff 17.0 cited
Remove retry loop in heap_page_prune().
- 1ccc1e05ae8f 17.0 cited
vacuumlazy.c: document vistest and OldestXmin.
- 73f6ec3d3c8d 15.0 cited
Deduplicate choice of horizon for a relation procarray.c.
- d9d8aa9bb9aa 15.0 cited
Remove tupgone special case from vacuumlazy.c.
- 8523492d4e34 14.0 cited
Simplify state managed by VACUUM.
- b4af70cb2103 14.0 cited
Recycle nbtree pages deleted during same VACUUM.
- 9dd963ae2534 14.0 cited
snapshot scalability: Don't compute global horizons while building snapshots.
- dc7420c2c927 14.0 cited
Raise error when affecting tuple moved into different partition.
- f16241bef7cc 11.0 cited

Attachments

v1-0001-Fix-vacuum-hang.patch (text/x-patch) patch v1-0001

On Sun, May 12, 2024 at 11:19 PM Bowen Shi <zxwsbg12138@gmail.com> wrote:
>
> Hi,
>>
>> Obviously we should actually fix this on back branches, but could we
>> at least make the retry loop interruptible in some way so people could
>> use pg_cancel/terminate_backend() on a stuck autovacuum worker or
>> vacuum process?
>
>
> If the problem happens in versions <= PG 16, we don't have a good solution (vacuum process holds the exclusive lock cause checkpoint hangs).
>
> Maybe we can make the retry loop interruptible first. However, since we are using START_CRIT_SECTION, we cannot simply use CHECK_FOR_INTERRUPTS to handle it.

As far as I can tell, in 14 and 15, the versions where the issue
reported here is present, there is not a critical section in the
section of code looped through in the retry loop in lazy_scan_prune().
We can actually fix the particular issue I reproduced with the
attached patch. However, I think it is still worth making the retry
loop interruptible in case there are other ways to end up infinitely
looping in the retry loop in lazy_scan_prune().

- Melanie