Horton

Re: BUG #17255: Server crashes in index_delete_sort_cmp() due to race condition with vacuum

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Dmitry Dolgov <9erthalion6@gmail.com>, Alexander Lakhin <exclusion@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Date: 2021-11-19T00:36:23Z
Lists: pgsql-bugs

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Hi,

On 2021-11-17 23:19:41 -0800, Andres Freund wrote:
> Not sure if it's worth it, but I think this can be made into a reliably
> isolationtest by causing a tables index to locked exclusively, blocking
> vac_open_indexes(), which can then reliably schedule a new relcache inval,
> which in turn can compute a new RecentXmin. Might be too fragile to be worth
> it.

Attached is such an isolationtest. In an unmodified HEAD it ends up with

step s1_select_1:
  SET LOCAL enable_seqscan = false;
  SELECT ctid, /*xmin, xmax, */ id FROM many_updates WHERE id = 1;
  RESET enable_seqscan;

ctid |id
-----+--
(0,3)|17
(1 row)

without amcheck detecting corruption at that point:(.


It's clearly not yet something we could consider committable, but I think it
might be a useful basis for such a test.

Greetings,

Andres Freund

Commits

  1. vacuumlazy.c: Standardize rel_pages terminology.

  2. vacuumlazy.c: document vistest and OldestXmin.

  3. heap pruning: Only call BufferGetBlockNumber() once.

  4. Fix possible HOT corruption when RECENTLY_DEAD changes to DEAD while pruning.

  5. Assert redirect pointers are sensible after heap_page_prune().

  6. Remove tupgone special case from vacuumlazy.c.

  7. Recycle nbtree pages deleted during same VACUUM.

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

  9. Refactor heap_page_prune so that instead of changing item states on-the-fly,