Re: Remove xmin and cmin from frozen tuples

On Sat, Sep 03, 2005 at 10:59:31AM +0200, Manfred Koizar wrote:
> On Fri, 2 Sep 2005 20:41:48 -0400 (EDT), Bruce Momjian
> <pgman@candle.pha.pa.us> wrote:
> >> Once I had a patch based on 7.4 that stored cmin and cmax in
> >> backend-local memory.
> 
> >Interesting idea, but how would you record the cmin/xmin values without
> >requiring unlimited memory?
> 
> That's exactly the reason for not sending it to -patches.  Without
> spilling to disk this is just not ready for real life.  The problem is
> that -- unlike other data structures that build up during a
> transaction, e.g. trigger queues -- cmin/cmax lookup requires random
> access, so we'd need some form of tree or hash.  Unfornunately I never
> got beyond brainstorming :-(
> 
> BTW, is there anything else that'd need spilling to disk during long
> transactions?

Yes, the queue of pending deferred triggers.

-- 
Alvaro Herrera -- Valdivia, Chile         Architect, www.EnterpriseDB.com
"El hombre nunca sabe de lo que es capaz hasta que lo intenta" (C. Dickens)