Re: Slightly OT.

On Sat, Jun 02, 2007 at 01:30:53AM +0200, Alexander Staubo wrote:

> There needs to be a point of synchronization when a DDL transaction
> appears that blocks further write transactions from running. As far as
> I can tell, the slaves themselves can continue to receive pending
> events, but perhaps not.

In order to do it automatically, you have to lock everyone, get all
the events through, and then perform the DDL, and then come out of
lock. Otherwise, what happens when you do DROP COLUMN? If it goes
through ahead of data that ought to go into that column, you have
just broken your cluster. I suppose you could figure out a way to
work around this, but pretty soon you are building an artificial
intelligence expert system with event-predicting capabilities. Such
systems are not well known for their simplicity and ease of
maintenance.

> Last I checked, nobody was actually terribly *happy* about having to
> pipe schema changes through slonik.

Nobody would suggest it's the friendliest arrangement. But this is a
field where the details really count, and therefore proposals to make
it more friendly have to account for how that friendliness in a lot
of cases doesn't lead to complete breakage in others. (I had to be
exposed to the multimaster MS SQL stuff, years ago, and I have to say
that it was great when it worked; but when things went south, boy did
your life suck. Whether it is better now, I don't know.)

A
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