On Wed, 16 Feb 2022 at 20:54, Peter Geoghegan <p...@bowt.ie> wrote: > > On Tue, Feb 15, 2022 at 10:48 AM Matthias van de Meent > <boekewurm+postg...@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).
Good catch, it is not. Attached a version that re-establishes maxoff after each prune operation. -Matthias
v8-0001-Improve-application-of-line-pointer-array-truncat.patch
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