wrong query results on bf leafhopper

Hi,

I noticed this recent BF failure:
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=leafhopper&dt=2025-05-15%2008%3A10%3A04

=== dumping /home/bf/proj/bf/build-farm-17/HEAD/pgsql.build/src/test/recovery/tmp_check/regression.diffs ===
diff -U3 /home/bf/proj/bf/build-farm-17/HEAD/pgsql.build/src/test/regress/expected/memoize.out /home/bf/proj/bf/build-farm-17/HEAD/pgsql.build/src/test/recovery/tmp_check/results/memoize.out
--- /home/bf/proj/bf/build-farm-17/HEAD/pgsql.build/src/test/regress/expected/memoize.out 2025-05-15 08:10:04.211926695 +0000
+++ /home/bf/proj/bf/build-farm-17/HEAD/pgsql.build/src/test/recovery/tmp_check/results/memoize.out 2025-05-15 08:18:29.117733601 +0000
@@ -42,7 +42,7 @@
-> Nested Loop (actual rows=1000.00 loops=N)
-> Seq Scan on tenk1 t2 (actual rows=1000.00 loops=N)
Filter: (unique1 < 1000)
- Rows Removed by Filter: 9000
+ Rows Removed by Filter: 8982
-> Memoize (actual rows=1.00 loops=N)
Cache Key: t2.twenty
Cache Mode: logical
@@ -178,7 +178,7 @@
-> Nested Loop (actual rows=1000.00 loops=N)
-> Seq Scan on tenk1 t1 (actual rows=1000.00 loops=N)
Filter: (unique1 < 1000)
- Rows Removed by Filter: 9000
+ Rows Removed by Filter: 8981
-> Memoize (actual rows=1.00 loops=N)
Cache Key: t1.two, t1.twenty
Cache Mode: binary

For a moment I thought this could be a bug in memoize, but that doesn't
actually make sense - the failure isn't in memoize, it's the seqscan.

Subsequently I got worried that this is an AIO bug or such causing wrong query
results. But there are instances of this error well before AIO was
merged. E.g.
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=leafhopper&dt=2024-12-18%2023%3A35%3A04

The same error is also present down to 16.

In 15, I saw a potentially related error
https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=leafhopper&dt=2024-12-16%2023%3A43%3A03

There have been other odd things on leafhopper, see e.g.:
https://www.postgresql.org/message-id/35d87371-f3ab-42c8-9aac-bb39ab5bd987%40gmail.com
https://postgr.es/m/Z4npAKvchWzKfb_r%40paquier.xyz

Greetings,

Andres Freund