Re: serializable lock consistency

On Mon, Dec 20, 2010 at 7:19 PM, Florian Pflug <fgp(at)phlo(dot)org> wrote:
>> Space in the tuple header is
>> precious, and I am not at all convinced that we should be willing to
>> surrender any for this.
>
> Thats a pretty tight space to maneuver in, though. So tight, in fact,
> that I may as well give up, barring some absolutely genius idea, which
> I don't even know where to look for at the moment.
>
> Every feature has its price, and if giving up on completely hypothetical
> future savings is too costly, then surely anything else I might suggest
> is too :-(

Of the ideas proposed so far, the idea of somehow making use of the
existing multi-xid machinery to do this seems the most promising to
me. But I haven't yet understood exactly what you're proposing, or
fully thought through the performance implications, which is obviously
something that needs to happen, and if that doesn't pan out, then, as
I said upthread and you said here, yeah, we may need a new idea.

It would be useful if some other folks weighed in on this, too. I
understand what behavior we're trying to get here and why we want
that, but I don't necessarily have the greatest understanding of all
the details of the on-disk format.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company