Re: Compression and on-disk sorting

On Tue, May 16, 2006 at 04:50:22PM -0500, Jim C. Nasby wrote:
> > I had a look at this. At first glance it doesn't seem too hard, except
> > the whole logtape process kinda gets in the way. If it wern't for the
> > mark/restore it'd be trivial. Might take a stab at it some time, if I
> > can think of a way to handle the seeking...
>
> Oh, do we need to randomly seek? Is that how we switch from one tape to
> another?

Not seek, mark/restore. As the code describes, sometimes you go back a
tuple. The primary reason I think is for the final pass, a merge sort
might read the tuples multiple times, so it needs to support it there.

> It might be easier to switch to giving each tape it's own file...

I don't think it would make much difference. OTOH, if this turns out to
be a win, the tuplestore could have the same optimisation.

Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.