Horton

Re: relfrozenxid may disagree with row XIDs after 1ccc1e05ae

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Bowen Shi <zxwsbg12138@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, Noah Misch <noah@leadboat.com>, Alexander Lakhin <exclusion@gmail.com>, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Date: 2024-05-16T20:29:49Z
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 →

  1. Ensure vacuum removes all visibly dead tuples older than OldestXmin

  2. Combine freezing and pruning steps in VACUUM

  3. Handle non-chain tuples outside of heap_prune_chain()

  4. Fix false reports in pg_visibility

  5. Remove retry loop in heap_page_prune().

  6. vacuumlazy.c: document vistest and OldestXmin.

  7. Deduplicate choice of horizon for a relation procarray.c.

  8. Remove tupgone special case from vacuumlazy.c.

  9. Simplify state managed by VACUUM.

  10. Recycle nbtree pages deleted during same VACUUM.

  11. snapshot scalability: Don't compute global horizons while building snapshots.

  12. Raise error when affecting tuple moved into different partition.

Hi,

On 2024-05-16 16:13:35 -0400, Peter Geoghegan wrote:
> On Thu, May 16, 2024 at 3:39 PM Andres Freund <andres@anarazel.de> wrote:
> > Melanies reproducer works because there are catalog accesses that can trigger
> > a recomputation of fuzzy horizon. For testing the "easy" window for that is
> > the vac_open_indexes() < 16, because it happens after determining the horizon,
> > but before actually vacuuming.
>
> What about the call to GetOldestNonRemovableTransactionId() that takes
> place in _bt_pendingfsm_finalize()?

Ah, good catch! That'd do it.



> > Now I wonder if there is some codepath triggering catalog lookups during bulk
> > delete.
>
> I don't think that there's any rule that says that VACUUM cannot do
> catalog lookups during bulk deletions. B-Tree page deletion needs to
> generate an insertion scan key, so that it can "refind" a page
> undergoing deletion. That might require catalog lookups.

I'm not saying there's a hard rule against it. Just that there wasn't an
immediately apparent, nor immediately observable, path for it. As I didn't see
the path to the horizon recomputation, I didn't know how a btbulkdelete in the
middle of the scan would potentially trigger the problem.

Greetings,

Andres Freund