On Thu, 18 Dec 2025 at 20:18, Melanie Plageman <[email protected]> wrote:
> But you are right, I don't see any non-error code path where a heap > page would become empty (all line pointers set unused) and then not be > set all-visible. Only vacuum sets line pointers unused and if all the > line pointers are unused it will always set the page all-visible. > > I think, though, that if we error out in lazy_scan_prune() after > returning from heap_page_prune_and_freeze() such that we don't set the > empty page all-visible, we can end up with an empty page without > PD_ALL_VISIBLE set. You can see how this might work by patching the VM > set code in lazy_scan_prune() to skip empty pages. > Thank you for your explanation! I completely forgot that PD_ALL_VIS is a non-persistent change (hint bit). so its update can be trivially lost. The simplest real-life example is being killed just after returning from heap_page_prune_and_freeze, yes. PFA tap test covering lazy_scan_new_or_empty code path for empty-but-not-all-visible page -- Best regards, Kirill Reshke
v1-0001-Add-TAP-test-for-empty-page-vacuum.patch
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