Re: Should FLUSH TABLES WITH READ LOCK wait for updating transactions?

[Baron Schwartz]

Monty,

> To answer this one, we should consider what FLUSH TABLES is used for.
>
> It's main (only?) purposes are
>
> - To allow easy file system level backups of the databases
> - To prepare a database for a snapshot
> - (Optional) Flush things to disk, so that a restart is faster.

I have seen many people use it as a general-purpose write barrier.
For example, in Alex Davies's new High Availability Cookbook, he
suggests using it before SET GLOBAL read_only = 1, to be sure the
change has really taken effect for all connections when performing a
failover.