Re: Deriving Recovery Snapshots

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.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com