[RndTbl] mysql update delays when no rows match, when backup running

[Trevor Cordes]

On 2023-02-04 Scott Toderash wrote:
> Assuming you use mysqldump. It does lock tables. If it didn't then
> data could change while the backup of that table is happening,
> producing unpredictable results.
> 
> You could set up MySQL replication to another machine and run your 
> backup on that one instead. That scenario would avoid the delay you
> are seeing but seems like a lot of trouble for this unless you need 
> constantly consistent performance.

Doh!  I didn't see your reply as for some reason it wasn't in the
thread.  I need to eyeball things more carefully.

Glad you thought up the same replication idea that dawned on me in the
interim.

And yes, I needed to also consider the implications on not doing a full
db-wide lock.  I think the new transactional method Adam found will
achieve the same thing as a db-wide lock without actually doing a
db-wide lock: it looks like the xaction will be initiated db-wide (i.e.
once for the whole db).