galera.galera_change_user fails: output has an extra "change_user user1,,;" line after "# After COM_CHANGE_USER"

galera.galera_change_user fails on the 12.3, 13.1 and main (13.2) branches: the output has a change_user user1,,; line after # After COM_CHANGE_USER that r/galera_change_user.result does not contain.

Build Run Info

Failure text

Latest run on 13.1 (worker number, timestamps and paths differ between runs; the latest runs on 12.3 and main show the same added line):

galera.galera_change_user                w5 [ fail ]

        Test ended at 2026-11-02 04:30:06

CURRENT_TEST: galera.galera_change_user

--- /home/buildbot/s390x-ubuntu-2204/build/mysql-test/suite/galera/r/galera_change_user.result	2026-11-01 22:30:05.000000000 +0000

+++ /home/buildbot/s390x-ubuntu-2204/build/mysql-test/suite/galera/r/galera_change_user.reject	2026-11-02 04:29:55.861927364 +0000

@@ -21,6 +21,7 @@

 0

 include/assert.inc [SELECT did a causal read on a fresh connection]

 # After COM_CHANGE_USER

+change_user user1,,;

 SET SESSION wsrep_sync_wait = 1;

 SELECT COUNT(*) FROM test.t1;

 COUNT(*)

Result length mismatch

 - saving '/home/buildbot/s390x-ubuntu-2204/build/mysql-test/var/5/log/galera.galera_change_user/' to '/home/buildbot/s390x-ubuntu-2204/build/mysql-test/var/log/galera.galera_change_user/'

Retrying test galera.galera_change_user, attempt(2/3)...

Analysis

The test file is identical on 10.11, 11.4, 11.8, 12.3, 13.1 and main and calls change_user 'user1' three times. On 12.3 and later the output echoes change_user user1,,; for each call; the result files of 10.11, 11.4 and 11.8 hold no echo lines, and no failure of this test is recorded on those branches. On 12.3, 13.1 and main r/galera_change_user.result records the echo for the first two calls but not for the third one, which belongs to the section that MDEV-41385 (commit fb32a71fdea6, https://github.com/MariaDB/server/pull/5814) added to the test and the result file. That section reached 12.3 with the merge commit ffaba7b55c7f (2026-10-22), and the result file on 12.3, 13.1 and main has been the same since. Between 2026-10-12 and 2026-11-02 the failure was recorded 368 times (76 on release branches: 12.3 29, 13.1 40, main 7), the first one on that merge commit itself (branch bb-12.3-knielsen, 2026-10-22) and none in the ten days before it; the first and the latest failing build of each of 12.3, 13.1 and main contain the merge commit. Eight builders report the failure (s390x-ubuntu-2204, ppc64le-ubuntu-2204, aarch64-debian-12, aarch64-debian-13, amd64-freebsd-14, amd64-last-N-failed, amd64-debian-12-deb-autobake-migration and amd64-rhel-9-rpm-autobake-migration; the two autobake-migration builders store only the tail of the output, which shows the same line). The same diff on four CPU architectures points at the result file, not at a builder. The diff is this one added line, so the result file on 12.3 needs change_user user1,,; after # After COM_CHANGE_USER.

Created via the mtr-failure-create-bug skill.