Re: TRM and sorts
Date: Wed, 05 Sep 2007 15:22:19 GMT
Jonathan Leffler wrote:
> paul c wrote:
> It's been a couple of years (at least) since I read anything concrete
> about the TRM, but my impression was that all the columns were always
> sorted - so run-time sorts on single columns are unnecessary, and when
> you have to sort data on multiple columns, you should be able to
> preserve the order of the lead column of the sort, which should simplify
> the sorting (if only because you only have to sort each subrange with
> the same lead column).
> Am I wrong on that?
I'm pretty sure you are right, although I guess with enough added structure those "subrange" sorts could be replaced with "merges" since there would always be a structure that would order each attribute's values (which would make a memory-only version much fatter). I mentioned only "ORDERing", but "GROUPing" operations might be affected more in some apps. It just seemed a little ironic to me that after going to all the trouble to pre-sort or indexing every attribute, some run-time sorting might still be needed.
p Received on Wed Sep 05 2007 - 17:22:19 CEST