Sometimes users ask for something that doesn’t really make sense.
On the first glance. But then you start asking and realize that
the user was right, you were wrong, and it is, actually, a
perfectly logical and valid use case.
I’ve had one of these moments when I’ve heard about a request of
making triggers to work on the slave in the row-based
replication. Like, really? In RBR all changes made by triggers
are replicated from the master to slaves as row events. If
triggers would be fired on the slave they would do their changes
twice. And anyway, assuming that one only has triggers one the
slave (why?) in statement-based replication triggers would run on
the slave normally, wouldn’t they?
Well, yes, they would, but one cannot always use statement-based
replication. If one could, RBR would’ve never been implemented.
There are many cases that statement-based replication cannot
handle correctly. Galera requires RBR too. And as …[Read more]