Re: BUG #17257: (auto)vacuum hangs within lazy_scan_prune()

Peter Geoghegan <pg@bowt.ie>

From: Peter Geoghegan <pg@bowt.ie>

To: Noah Misch <noah@leadboat.com>

Cc: Matthias van de Meent <boekewurm+postgres@gmail.com>, robertmhaas@gmail.com, Alexander Lakhin <exclusion@gmail.com>, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>, Andres Freund <andres@anarazel.de>

Date: 2024-01-09T20:59:19Z

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

On Sat, Jan 6, 2024 at 3:24 PM Noah Misch <noah@leadboat.com> wrote:
> On Sun, Dec 31, 2023 at 03:53:34PM -0800, Peter Geoghegan wrote:
> > I am aware of a production database that appears to run into the same
> > problem. Inserts and concurrent cross-partition updates are used
> > heavily on this instance (the table in question uses partitioning).
> > Perhaps you happened upon a similar problematic production database,
> > and found this thread when researching the issue? Maybe we've both
> > seen the same problem in the wild?
>
> I did find this thread while researching the symptoms I was seeing.  No
> partitioning where I saw them.

I'm starting to think that partitioning was just a red herring. The
instance had problems in the presence of DELETEs, not UPDATEs (or
cross-partition UPDATEs).

Did the affected system that you investigated happen to have an
atypically high number of databases? The system 15.4 system that I saw
the problem on had almost 3,000 databases.

-- 
Peter Geoghegan