CTAS conflict with DDL can cause node hanging

if create table as select runs in parallel with DDL statement operating on the select table, it can happen that CTAS processing remains hanging.

The problem relates to rollback of the CTAS, which involves rolling back both the transaction (of insert statements) and create table. It turns out that the table is not always dropped during this rollback and this causes issues later on.

The problem was first observed by RQG percona_qa run against one PXC node, but it is also possible to reproduce by two clients, where one runs: "CREATE TABLE t1 AS SELECT * FROM t2" and the other runs: "TRUNCATE t2;