Re: BUG: Postgres 14 + vacuum_defer_cleanup_age + FOR UPDATE + UPDATE

Hi,

On 2023-02-06 13:02:05 -0800, Andres Freund wrote:
> I didn't quite feel confident pushing a fix for this just before a minor
> release, so I'll push once the minor releases are tagged. A quite minimal fix
> to GetFullRecentGlobalXmin() in 12-13 (returning FirstNormalTransactionId if
> epoch == 0 and RecentGlobalXmin > nextxid_xid), and the slightly larger fix in
> 14+.

Pushed that.


Mark:

I worked some more on the fixes for amcheck, and fixes for amcheck.

The second amcheck fix ends up correcting some inaccurate output in the tests
- previously xids from before xid 0 were reported to be in the future.

Previously there was no test case exercising exceeding nextxid, without
wrapping around into the past. I added that at the end of
004_verify_heapam.pl, because renumbering seemed too annoying.

What do you think?


Somewhat random note:

Is it intentional that we VACUUM FREEZE test ROWCOUNT times? That's
effectively O(ROWCOUNT^2), albeit with small enough constants to not really
matter. I don't think we need to insert the rows one-by-one either. Changing
that to a single INSERT and FREEZE shaves 10-12% off the tests.  I didn't
change that, but we also fire off a psql for each tuple for heap_page_items(),
with offset $N no less. That seems to be another 500ms.

Greetings,

Andres Freund