Comment 1 for bug 1357003

Some additional information. I asked Morgan (upstream):

> For 12.04 or 14.04 specifically, are there real benefits of making this
> change? Even if people are doing it wrong already, is it right to
> suddenly break them if they haven't already noticed a problem? What
> impact will the breakage have to them, if any? Will they be angry about
> that?

We are not aware of any "correct" use case for SET GLOBAL sql_log_bin=x.

i.e. Some users may use it to emulate disabling the binary log, but
since this only applies to new sessions it is not reliable, and is not
fit for this purpose. Another situation might be to start the server
with binary logging disabled, then enable it with SET GLOBAL
sql_log_bin=0, but the same unreliability applies.

> For example, say someone is doing it wrong at the moment, but it doesn't
> impact him directly. With this change, a script he's running suddenly
> breaks, and that failure cascades into some kind of production downtime.
> Could this happen?

That is not impossible, but very unlikely. If their current script does
this, their slaves are now out of sync.

Hence the dilemma where we are needing to be more drastic.