Re: Page Checksums + Double Writes

On 12/23/11, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Dec 23, 2011 at 11:14 AM, Kevin Grittner
> <Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>> Thoughts?
>
> Those are good thoughts.
>
> Here's another random idea, which might be completely nuts. Maybe we
> could consider some kind of summarization of CLOG data, based on the
> idea that most transactions commit.

I had a perhaps crazier idea. Aren't CLOG pages older than global xmin
effectively read only? Could backends that need these bypass locking
and shared memory altogether?

> An obvious problem is that, if the abort rate is significantly
> different from zero, and especially if the aborts are randomly mixed
> in with commits rather than clustered together in small portions of
> the XID space, the CLOG rollup data would become useless. On the
> other hand, if you're doing 10k tps, you only need to have a window of
> a tenth of a second or so where everything commits in order to start
> getting some benefit, which doesn't seem like a stretch.

Could we get some major OLTP users to post their CLOG for analysis? I
wouldn't think there would be much security/propietary issues with
CLOG data.

Cheers,

Jeff