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: 2022-03-11T03:46:32Z
Lists: pgsql-bugs 
Hi,

On 2022-03-10 19:40:21 -0800, Peter Geoghegan wrote:
> On Thu, Mar 10, 2022 at 7:13 PM Andres Freund <andres@anarazel.de> wrote:
> > > 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.

I'm not talking about just moving the vistest acquisition, but also
vacuum_set_xid_limits(). Which obviously *does* benefit from delaying as long
as possible.


> > 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.

Cool.

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,