Re: Big 7.4 items

Neil Conway wrote:
> On Fri, 2002-12-13 at 13:36, Jan Wieck wrote:
> > But you cannot use the result of such a SELECT to update anything. So
> > you can only phase out complete read only transaction to the slaves.
> > Requires support from the application since the load balancing system
> > cannot know automatically what will be a read only transaction and what
> > not.
>
> Interesting -- SQL contains the concept of "read only" and "read write"
> transactions (the default is RW). If we implemented that (which
> shouldn't be too difficult[1]), it might make differentiating between
> classes of transactions a little easier. Client applications would still
> need to be modified, but not nearly as much.
>
> Does this sound like it's worth doing?
>
> [1] -- AFAICS, the only tricky implementation detail is deciding exactly
> which database operations are "writes". Does nextval() count, for
> example?

You can't migrate a session between nodes, so the entire _session_ has
to be read-only.

--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073