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

Hi,

On 2021-11-10 13:40:25 -0800, Peter Geoghegan wrote:
> On Wed, Nov 10, 2021 at 1:04 PM Peter Geoghegan <pg@bowt.ie> wrote:
> > On Wed, Nov 10, 2021 at 11:20 AM Andres Freund <andres@anarazel.de> wrote:
> > > The way this definitely breaks - I have been able to reproduce this in
> > > isolation - is when one tuple is processed twice by heap_prune_chain(), and
> > > the result of HeapTupleSatisfiesVacuum() changes from
> > > HEAPTUPLE_DELETE_IN_PROGRESS to DEAD.
> >
> > I had no idea that that was now possible. I really think that this
> > ought to be documented centrally.
> 
> BTW, is it just a coincidence that we have only seen these problems
> with pg_class? Or does it have something to do with the specifics of
> VISHORIZON_CATALOG/horizons.catalog_oldest_nonremovable, or something
> else along those lines?

It's the testcase. The test instructions specify autovacuum=off and only
pg_class is vacuumed. There are a other hot updates than to pg_class, but
there's much less HOT pruning on them because there's no loop of VACUUMs.

Greetings,

Andres Freund