Re: [PATCH 10/16] Introduce the concept that wal has a 'origin' node

On Monday, June 18, 2012 11:51:27 PM Daniel Farina wrote:
> On Mon, Jun 18, 2012 at 8:50 AM, Andres Freund <andres(at)2ndquadrant(dot)com>
wrote:
> >> * Size of field. 16 bits is enough for 32,000 master nodes, which is
> >> quite a lot. Do we need that many? I think we may have need for a few
> >> flag bits, so I'd like to reserve at least 4 bits for flag bits, maybe
> >> 8 bits. Even if we don't need them in this release, I'd like to have
> >> them. If they remain unused after a few releases, we may choose to
> >> redeploy some of them as additional nodeids in future. I don't foresee
> >> complaints that 256 master nodes is too few anytime soon, so we can
> >> defer that decision.
> >
> > I wished we had some flag bits available before as well. I find 256 nodes
> > a pretty low value to start with though, 4096 sounds better though, so I
> > would be happy with 4 flag bits. I think for cascading setups and such
> > you want to add node ids for every node, not only masters...
> >
> > Any opinions from others on this?
>
> What's the cost of going a lot higher? Because if one makes enough
> numerical space available, one can assign node identities without a
> coordinator, a massive decrease in complexity.
It would increase the size of every wal record. We just have 16bit left there
by chance...

Andres
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