Re: Compression and on-disk sorting

On Tue, May 16, 2006 at 09:24:38AM +0200, Zeugswetter Andreas DCP SD wrote:
> 
> > > Given that any time that happens we end up caring much less about
> CPU
> > > usage and much more about disk IO, for any of these cases that use
> > > non-random access, compressing the data before sending it to disk
> would
> > > potentially be a sizeable win.
> > 
> > Note however that what the code thinks is a spill to disk and what
> > actually involves disk I/O are two different things.  If you think
> > of it as a spill to kernel disk cache then the attraction is a lot
> > weaker...
> 
> Yes, that is very true. However it would also increase the probability
> that spill to disk is not needed, since more data fits in RAM.

That's a pretty thin margin though, depending on how good the
compression is. This also assumes that you have a compression algorithm
that supports random access.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461