Re: Deriving Recovery Snapshots

On Thu, 2008-10-23 at 08:40 +0300, Heikki Linnakangas wrote:
> Simon Riggs wrote:
> > On Wed, 2008-10-22 at 21:47 +0100, Simon Riggs wrote:
> >
> >> But once you reach 64 transactions, you'll need to write an extra WAL
> >> record for every subtransaction, which currently I've managed to avoid.
> >
> > Yes, I've managed to avoid it, but it will simplify the patch if you
> > think its not worth bothering with. This won't really effect anybody
> > I've met running straight Postgres, but it may effect EDB. It's not a
> > problem for me, but I was second guessing objections.
> >
> > If I do that then I can just pass the slotId in full on every WAL
> > record, which simplifies a couple of other things also.
> >
> > So, does everybody accept that we will write a WAL record for every
> > subtransaction assigned, once we hit the size limit of the subxid cache?
> > i.e. currently 65th subxid and beyond.
>
> Would have to see the patch to understand what the code simplicity vs.
> extra WAL logging tradeoff really is.

Well, if your not certain now, then my initial feeling was correct. I
don't think everybody would agree to that. The code simplification would
be real, but I don't think it's that hard now.

--
Simon Riggs www.2ndQuadrant.com
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