Re: [Maria-developers] caec6b4b3d7: MDEV-17573 Assertion in federatedx on multi-update

Hi, Aleksey! Looks reasonable to me. MYSQL_RES is stored in the handler. Of course, MYSQL_ROWS *current, which is a pointer into MYSQL_RES, has to be in the handler, it cannot be shared. Ok to push, thanks! On Oct 23, Aleksey Midenkov wrote:

revision-id: caec6b4b3d7 (mariadb-10.3.21-250-gcaec6b4b3d7) parent(s): a00c668ddf2 author: Aleksey Midenkov committer: Aleksey Midenkov timestamp: 2020-10-21 13:38:37 +0300 message:

MDEV-17573 Assertion in federatedx on multi-update

Cause: shared federatedx_io cannot store table-specific data.

Fix: move current row reference `federatedx_io_mysql::current` to ha_federatedx.

FederatedX connection (represented by federatedx_io) is stored into federatedx_txn::txn_list of per-server connections (see federatedx_txn::acquire()). federatedx_txn object is stored into THD (see ha_federatedx::external_lock()). When multiple handlers acquire FederatedX connection they get single federatedx_io instance. Multiple handlers do their operation via federatedx_io_mysql::mark_position() and federatedx_io_mysql::fetch_row() in arbitrarty manner. They access the same federatedx_io_mysql instance and same MYSQL_ROWS *current pointer, so one handler disrupts the work of the other.

Related to "MDEV-14551 Can't find record in table on multi-table update with ORDER BY".

Regards, Sergei VP of MariaDB Server Engineering and security@mariadb.org