Horton

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

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Andres Freund <andres@anarazel.de>
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: 2021-11-13T02:32:48Z
Lists: pgsql-bugs 
On Fri, Nov 12, 2021 at 5:57 PM Peter Geoghegan <pg@bowt.ie> wrote:
> You said it yourself: who knows exactly what the justification for
> RECENTLY_DEAD->DEAD was? I have to imagine it had something to do with the
> "INSERT_IN_PROGRESS becomes DEAD due to concurrent xact abort" thing,
> but that's unclear. And even if it was clear, and even if we knew that
> it was 100% safe at one point, it still wouldn't be clear that it's
> safe today, in Postgres 14.

Another relevant factor is how we deal with already-corrupt HOT chains
affected by the bug. I would be comfortable with a full "can't happen"
error in the new code path for disconnected and aborted heap-only
tuples, provided the error only gets raised when the tuple is fully
LIVE according to HTSV (and also assert that it's DEAD). Something
like my v4 plus this LIVE-should-be-DEAD defensive error seems very
likely to avoid making the corruption any worse. There is a huge
amount of redundancy in the tuple headers that we can cross check
inexpensively.

-- 
Peter Geoghegan

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,