Re: Lowering the ever-growing heap->pd_lower

On Tue, Feb 15, 2022 at 10:48 AM Matthias van de Meent
<boekewurm+postgres@gmail.com> wrote:
> Peter Geoghegan asked for good arguments for the two changes
> implemented. Below are my arguments detailed, with adversarial loads
> that show the problematic behaviour of the line pointer array that is
> fixed with the patch.

Why is it okay that lazy_scan_prune() still calls
PageGetMaxOffsetNumber() once for the page, before it ever calls
heap_page_prune()? Won't lazy_scan_prune() need to reestablish maxoff
now, if only so that its scan-page-items loop doesn't get confused
when it goes on to read "former line pointers"? This is certainly
possible with the CLOBBER_FREED_MEMORY stuff in place (which will
memset the truncated line pointer space with a 0x7F7F7F7F pattern).

-- 
Peter Geoghegan