Re: pg14b1 stuck in lazy_scan_prune/heap_page_prune of pg_statistic

Matthias van de Meent <boekewurm+postgres@gmail.com> writes:
> On Sun, 6 Jun 2021 at 18:35, Justin Pryzby <pryzby@telsasoft.com> wrote:
>> However, I also found an autovacuum chewing 100% CPU, and it appears the
>> problem is actually because autovacuum has locked a page of pg-statistic, and
>> every other process then gets stuck waiting in the planner.  I checked a few
>> and found these:

> My suspicion is that for some tuple on that page
> HeapTupleSatisfiesVacuum() returns HEAPTUPLE_DEAD for a tuple that it
> thinks should have been cleaned up by heap_page_prune, but isn't. This
> would result in an infinite loop in lazy_scan_prune where the
> condition on vacuumlazy.c:1800 will always be true, but the retry will
> not do the job it's expected to do.

Since Justin's got a debugger on the process already, it probably
wouldn't be too hard to confirm or disprove that theory by stepping
through the code.

            regards, tom lane