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: 2022-01-14T02:15:49Z
Lists: pgsql-bugs 
On 2022-01-12 13:05:45 -0800, Peter Geoghegan wrote:
> On Wed, Jan 12, 2022 at 11:25 AM Andres Freund <andres@anarazel.de> wrote:
> > > Any blockers?
> >
> > I'm just struggling with / procrastinating on the commit message, tbh. The
> > whole issue is kinda complicated to explain... :/

After struggling some more, I *finally* pushed the fix and the new assertions.


Thanks for the bug report, investigation, review, etc!


> I think that it would make sense for the commit message to frame the
> problem as: pruneheap.c doesn't take sufficient care when traversing
> HOT chains to determine their full extent, for the purposes of
> pruning. There was a general lack of robustness, and the snapshot
> scalability work happened to run into that, resulting in hot chain
> corruption under very specific conditions.
>
> If I was in your position I think I would resist framing the problem
> in this way; I'd probably be concerned that it would come off as
> shifting the blame elsewhere. This high level explanation of things
> makes the most sense to me, though. Surely that's the most important
> thing.

Thanks!

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,