I have not managed to reproduce it with Galera replication. Tried the both cases from this MDEV and from MDEV-13708 (the last one by Sergei) on 10.3.9 (ca26f91bcaa21933147974c823852a2e1c2e2bd7) and 10.3.21 (a14544260c33dcdb057d2f62c4aab33cb09ebcb1).
piotrniz can you please provide exact version of Galera lib you were using during the crash? Don't have other ideas how to repeat it.

I have just re-verified that the problem exists:

1. mysql
   Welcome to the MariaDB monitor. Commands end with ; or \g.
   Your MariaDB connection id is 185136
   Server version: 10.3.17-MariaDB-0+deb10u1-log Debian 10

Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

MariaDB [(none)]> use xp.pl
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
MariaDB [xp.pl]> CREATE TABLE testMain (primid INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (primid)) ENGINE = InnoDB;
Query OK, 0 rows affected (1.006 sec)

MariaDB [xp.pl]> CREATE TABLE testRef (id INT UNSIGNED NOT NULL AUTO_INCREMENT, pid INT UNSIGNED, bitmap TINYINT UNSIGNED NOT NULL DEFAULT 0, bitmap5 TINYINT UNSIGNED GENERATED ALWAYS AS (bitmap&(1<<5)) VIRTUAL, PRIMARY KEY (id), FOREIGN KEY (pid) REFERENCES testMain (primid) ON DELETE CASCADE ON UPDATE CASCADE);
Query OK, 0 rows affected (1.131 sec)

MariaDB [xp.pl]> CREATE INDEX bitmap5 ON testRef(bitmap5) USING BTREE;
Query OK, 0 rows affected (2.045 sec)
Rekordów: 0 Duplikatów: 0 Ostrzeżeń: 0

MariaDB [xp.pl]> INSERT INTO testMain VALUES(0);
Query OK, 1 row affected (0.048 sec)

MariaDB [xp.pl]> SELECT * FROM testMain;
--------

--------

--------
1 row in set (0.000 sec)

MariaDB [xp.pl]> INSERT INTO testRef(pid) VALUES(3);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`xp.pl`.`testRef`, CONSTRAINT `testRef_ibfk_1` FOREIGN KEY (`pid`) REFERENCES `testMain` (`primid`) ON DELETE CASCADE ON UPDATE CASCADE)
MariaDB [xp.pl]> INSERT INTO testRef(pid) VALUES(2);
Query OK, 1 row affected (0.047 sec)

MariaDB [xp.pl]> DELETE FROM testMain WHERE primid=2;
ERROR 2013 (HY000): Lost connection to MySQL server during query
MariaDB [xp.pl]> quit

^C^C^C^C^CBye

Packages in use:
ii mariadb-server-10.3 1:10.3.17-0+deb10u1 amd64 MariaDB database server binaries
ii mariadb-server-core-10.3 1:10.3.17-0+deb10u1 amd64 MariaDB database core server files
ii galera-3 25.3.25-2 amd64 Replication framework for transactional applications

I have not reproduced it even on MariaDB 10.3.9 and 10.3.17 with galera-3 25.3.25.
But I observered the crash not just after the deletion, but after any other next command. See linked MDEV-21153 Galera: Replica nodes crash with signal 6 after indexed virtual columns and FK cascading deletes: WSREP has not yet prepared node for application use.
And I presume that root cause for these two similar bugs is the same.

• branch 10.3
• commit bf58ec77a1adaa653a0b044b950cf420f8c19de9

  CREATE TABLE testMain (primid INT UNSIGNED NOT NULL AUTO_INCREMENT, PRIMARY KEY (primid)) ENGINE = InnoDB;

  CREATE TABLE testRef (id INT UNSIGNED NOT NULL AUTO_INCREMENT, pid INT UNSIGNED, bitmap TINYINT UNSIGNED NOT NULL DEFAULT 0, bitmap5 TINYINT UNSIGNED GENERATED ALWAYS AS (bitmap&(1<<5)) VIRTUAL, PRIMARY KEY (id), FOREIGN KEY (pid) REFERENCES testMain (primid) ON DELETE CASCADE ON UPDATE CASCADE);

  CREATE INDEX bitmap5 ON testRef(bitmap5) USING BTREE;

  INSERT INTO testMain VALUES(0);

  INSERT INTO testRef(pid) VALUES(3);

  SELECT * FROM testMain;

  primid

  1

  SELECT * FROM testRef;

  id pid bitmap bitmap5

  1 3 0 0

Insert should fail as there is no parent for pid = 3. This is repeatable with no Galera enabled.

nikitamalyavin, you agreed to work on virtual column bugs. I would expect this to be repeatable on 10.2 as well.