[17:49:07.251] #   Failed test 'concurrent operations with REINDEX/CREATE INDEX CONCURRENTLY stderr /(?^:^$)/'
[17:49:07.251] #   at /tmp/cirrus-ci-build/contrib/amcheck/t/007_repack_concurrently.pl line 56.
[17:49:07.251] #                   'pgbench: error: client 0 script 0 aborted in command 6 query 0: ERROR:  out of background worker slots
[17:49:07.251] # HINT:  You might need to increase "max_worker_processes".
[17:49:07.251] # pgbench: error: Run was aborted due to an error in thread 0

-------------------

This one showed something goes wrong, the sum of the table is broken. It may be 0 because non-MVCC safe, but I checked the logs:

2026-01-12 18:41:11.656 UTC client backend[76247] 007_repack_concurrently.pl LOG:  statement: SELECT (490588) / 0;

And also

backend[54349] 007_repack_concurrently.pl ERROR:  could not create unique index "tbl_pkey_repacknew"
2026-01-12 18:41:12.477 UTC client backend[54349] 007_repack_concurrently.pl DETAIL:  Key (i)=(942) is duplicated.
2026-01-12 18:41:12.477 UTC client backend[54349] 007_repack_concurrently.pl STATEMENT:  REPACK (CONCURRENTLY) tbl;

https://cirrus-ci.com/task/4521496594350080 (single snapshot version)

https://cirrus-ci.com/task/6157569896480768 (single snapshot version)

[18:36:17.466] #   at /Users/admin/pgsql/contrib/amcheck/t/007_repack_concurrently.pl line 56.
[18:36:17.466] #                   'pgbench: error: client 21 script 0 aborted in command 31 query 0: ERROR:  division by zero
[18:36:17.466] # pgbench: error: Run was aborted due to an error in thread 2

---------------------

https://cirrus-ci.com/task/5682762788634624 (multiple snapshots)

 Failed test 'concurrent operations with REINDEX/CREATE INDEX CONCURRENTLY stderr /(?^:^$)/'
[18:02:06.938] #   at t/007_repack_concurrently.pl line 56.
[18:02:06.938] #                   'pgbench: error: client 6 aborted in command 4 (SQL) of script 0; perhaps the backend died while processing
[18:02:06.938] # pgbench: error: Run was aborted due to an error in thread 0
[18:02:06.938] # WARNING:  terminating connection because of crash of another server process