On Thu, Mar 24, 2022 at 2:40 PM Peter Geoghegan <p...@bowt.ie> wrote: > > > This is absolutely mandatory in the aggressive case, because otherwise > > > relfrozenxid advancement might be seen as unsafe. My observation is: > > > Why should we accept the same race in the non-aggressive case? Why not > > > do essentially the same thing in every VACUUM? > > > > Sure, that seems like a good idea. I think I basically agree with the > > goals of the patch. > > Great.
Attached is v12. My current goal is to commit all 3 patches before feature freeze. Note that this does not include the more complicated patch including with previous revisions of the patch series (the page-level freezing work that appeared in versions before v11). Changes that appear in this new revision, v12: * Reworking of the commit messages based on feedback from Robert. * General cleanup of the changes to heapam.c from 0001 (the changes to heap_prepare_freeze_tuple and related functions). New and existing code now fits together a bit better. I also added a couple of new documenting assertions, to make the flow a bit easier to understand. * Added new assertions that document OldestXmin/FreezeLimit/relfrozenxid invariants, right at the point we update pg_class within vacuumlazy.c. These assertions would have a decent chance of failing if there were any bugs in the code. * Removed patch that made DISABLE_PAGE_SKIPPING not force aggressive VACUUM, limiting the underlying mechanism to forcing scanning of all pages in lazy_scan_heap (v11 was the first and last revision that included this patch). * Adds a new small patch 0003. This just moves the last piece of resource allocation that still took place at the top of lazy_scan_heap() back into its caller, heap_vacuum_rel(). The work in 0003 probably should have happened as part of the patch that became commit 73f6ec3d -- same idea. It's totally mechanical stuff. With 0002 and 0003, there is hardly any lazy_scan_heap code before the main loop that iterates through blocks in rel_pages (and the code that's still there is obviously related to the loop in a direct and obvious way). This seems like a big overall improvement in maintainability. Didn't see a way to split up 0002, per Robert's suggestion 3 days ago. As I said at the time, it's possible to split it up, but not in a way that highlights the underlying issue (since the issue 0002 fixes was always limited to non-aggressive VACUUMs). The commit message may have to suffice. -- Peter Geoghegan
v12-0001-Set-relfrozenxid-to-oldest-extant-XID-seen-by-VA.patch
Description: Binary data
v12-0003-vacuumlazy.c-Move-resource-allocation-to-heap_va.patch
Description: Binary data
v12-0002-Generalize-how-VACUUM-skips-all-frozen-pages.patch
Description: Binary data
