Re: [Maria-developers] 7198e7c71fc: MDEV-15458 Segfault in heap_scan() upon UPDATE after ADD SYSTEM VERSIONING

Hi, Aleksey! On Dec 23, Aleksey Midenkov wrote:

revision-id: 7198e7c71fc (versioning-1.0.6-82-g7198e7c71fc) parent(s): 6be155757b7 author: Aleksey Midenkov committer: Aleksey Midenkov timestamp: 2018-12-20 13:25:00 +0300 message:

MDEV-15458 Segfault in heap_scan() upon UPDATE after ADD SYSTEM VERSIONING

* HA_EXTRA_REMEMBER_POS, HA_EXTRA_RESTORE_POS for HEAP storage engine * Versioning tests support

As far as I can see, there are two approaches to fixing this bug. And if we go the way of HA_EXTRA_REMEMBER_POS/HA_EXTRA_RESTORE_POS then your fix is good. But I'd still like to understand whether write_row is supposed to disturb the scan. Why should heap_write() overwrite info->current_ptr=pos and info->current_hash_ptr? Inserting a row doesn't happen at the "current position", so I don't quite understand why it modifies current_ptr at all. There is no functionality like "continue the scan from the last inserted row", right? It just doesn't make sense to me. Regards, Sergei Chief Architect MariaDB and security@mariadb.org