Comment 10 for bug 1321767

Indeed updating table without PK nor any other index was crashing PXC node in version 5.6.15, when wsrep_slave_threads>1. It is easy to reproduce - remove keys from sbtest table and run multi-threaded OLTP sysbench test. It will crash with:

BF-BF X lock conflict
RECORD LOCKS space id 485 page no 74 n bits 144 index `GEN_CLUST_INDEX` of table `db1`.`sbtest1` trx id 95033 lock_mode X locks rec but not gap
...
and very similar stack trace.

Since PXC 5.6.19, the abort was removed, so instead, we will see error log flooded with:

"2016-06-02 07:51:48 17146 [Note] WSREP: BF conflict, order: 41008 41009

BF-BF X lock conflict,mode: 1027 supremum: 0
conflicts states: my 0 locked 0
RECORD LOCKS space id 485 page no 82 n bits 144 index `GEN_CLUST_INDEX` of table `db1`.`sbtest1` trx id 93362 lock_mode X locks rec but
not gap
BF-BF lock conflict, locking: 1
RECORD LOCKS space id 485 page no 82 n bits 144 index `GEN_CLUST_INDEX` of table `db1`.`sbtest1` trx id 93363 lock_mode X locks rec but
not gap"

but nodes won't crash.

Still, using non-indexed tables in PXC/Galera is not supported and each table should have primary key.