I stumbled across better performance (kdb+ vs. Jd) in my own stuff: http://blog.vmchale.com/article/q-perf <http://blog.vmchale.com/article/q-perf>
Basically joins take longer (which I think makes sense?). It’s easy to imagine that selections and joins (on the ordered keys) are going to be faster since one can implement them differently. FWIW, my *assumption* is that q’s use of ordered keys is what makes it faster, not 100% sure. Cheers, Vanessa McHale > On Feb 1, 2022, at 4:31 PM, Elijah Stone <elro...@elronnd.net> wrote: > > 1. What is the efficiency gain from ordered keys? > > (In general, the more restrictive your semantics are, the more freedom you > have about implementing them, and hence the more efficient you can be. So > this doesn't make sense to me. > > Ordering keys may happen to be faster as an _implementation_ strategy in some > situations and given some access patterns, and in that case the > implementation should certainly use such a representation. But I do not > think forcing semantics is a good performance argument.) > > 2. It is possible to materialize arbitrary orderings on-demand by > indexing with an appropriately ordered array of keys. I do not think > this is a good argument for making the data inherently ordered. > > -E > > On Tue, 1 Feb 2022, Raul Miller wrote: > >> On Mon, Jan 31, 2022 at 9:16 PM Elijah Stone <elro...@elronnd.net> wrote: >>> I think not; keys should not be ordered. >> >> I think I need to disagree here. >> >> (1) K (and Q) have shown that you get great efficiencies with ordered keys. >> >> (2) Also, arrays require ordered data for meaningful operations. >> >> (3) Lack of order tends to introduce needlessly arbitrary distinctions. >> >> Now... we might want to support multiple concepts of order, but that's >> relatively straightforward. >> >> Thanks, >> >> -- >> Raul >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
