On Sun, Jun 1, 2025 at 12:07 PM Peter Geoghegan <p...@bowt.ie> wrote: > > Commit 052026c9b9 made heap_vacuum_rel call RelationGetNumberOfBlocks > before it calls vacuum_get_cutoffs -- it swapped the order. This is > wrong, as explained by an intact comment above the call to > vacuum_get_cutoffs. > > In short, there is now a brief window during which the relation can be > extended that'll allow heap pages with tuple headers < VACUUM's > OldestXmin to be created, which are overlooked by that same VACUUM > (they're beyond the same VACUUM's rel_pages). As a result of all this, > VACUUM might advance pg_class.relfrozenxid to a later/younger value > than a remaining/unfrozen XID value from one of these unscanned heap > pages.
Thanks for the report. That was a dumb mistake. There was no reason for me to move the line up as you can see in the diff -- it must have been unintentional. I'll push the fix tomorrow. I started to feel like I ought to write a TAP test, but I'm hesitant to add a whole new TAP test for a case when a comment should have been sufficient deterrent. - Melanie
