On Thu, Mar 24, 2022 at 8:56 PM Thomas Munro <thomas.mu...@gmail.com> wrote: > Interesting. IIUC your chaos gizmo shows that particular vacuum test > still failing on master, but that wouldn't happen in real life because > since 383f2221 it's a temp table. Your gizmo should probably detect > temp rels, as your comment says. I was sort of thinking that perhaps > if DISABLE_PAGE_SKIPPING is eventually made to do what its name sounds > like it does, we could remove TEMP from that test and it'd still pass > with the gizmo...
Why not just use VACUUM FREEZE? That should work, because it won't settle for a cleanup lock on any page with an XID < OldestXmin. And even if there were only LP_DEAD items on a page, that wouldn't matter either, because we don't need a cleanup lock to get rid of those anymore. And we consistently do all the same steps for rel truncation in the no-cleanup-lock path (lazy_scan_noprune) now. I think that DISABLE_PAGE_SKIPPING isn't appropriate for this kind of thing. It mostly just makes VACUUM not trust the visibility map, which isn't going to help. While DISABLE_PAGE_SKIPPING also forces aggressive mode, that isn't going to help either, unless you somehow also make sure that FreezeLimit is OldestXmin (e.g. by setting vacuum_freeze_min_age to 0). VACUUM FREEZE (without DISABLE_PAGE_SKIPPING) seems like it would do everything you want, without using a temp table. At least on the master branch. -- Peter Geoghegan
