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: 2022-03-11T03:40:21Z
Lists: pgsql-bugs 
On Thu, Mar 10, 2022 at 7:13 PM Andres Freund <andres@anarazel.de> wrote:
> > NB: I intend to commit this revision of the patch (or something pretty
> > close to it) in the next few days, barring any objections.
>
> WFM.

Cool.

> > On Wed, Mar 9, 2022 at 4:25 PM Andres Freund <andres@anarazel.de> wrote:
> > > I think it'd be nicer if we did the horizon determination after allocating
> > > space for dead tuples... But it's still better than today, so...
> >
> > Why would it be nicer?
>
> Large allocation can take a bit. Especially dead_item_alloc() sneakily
> initializes parallelism (which is darn ugly). Determining the horizon after
> doing expensive stuff gives you a slightly better horizon...

I'm confused. You recently said "I don't think the minor optimization
[delaying establishing vistest] does anything (which I had stated
wrongly at some point in this thread)". But you now seem to be saying
that delaying establishing vistest has at least some small value as an
optimization. At least in theory.

> The whole s/nblocks/rel_pages/ seems like it should be done separately.

I'll break the mechanical s/nblocks/rel_pages/ out into a dedicated
commit, then.

-- 
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,