Re: [HACKERS] Passing "direct" args of ordered-set aggs to the transition function
On Jan23, 2014, at 17:20 , Tom Lane wrote: > Florian Pflug writes: >> Is there a particular reason why the "direct" arguments of ordered-set >> aggregates are not passed to the transition function too? > > Because they have to be evaluated only once. > > I did consider evaluating them once at the start and saving the values, > but that's a bit problematic from a memory management standpoint. Yeah, that's what I had in mind. I not sure I understand that memory management problems you mention though - couldn't we just copy them to some appropriate memory context, say aggcontext? What I'm more concerned about is whether it'd still be possible to have ordered_set_transition and ordered_set_transition_multi work for all the ordered-set aggregates we currently have. But I have yet to wrap my head fully around the VARIADIC any ANY stuff that goes on there... > Still, if you have a good solution to that and the cycles to produce a > patch, it's not too late to reconsider. I concur that it's not that > hard to think of cases where it'd be useful. I'll see what I can do. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] Passing "direct" args of ordered-set aggs to the transition function
Florian Pflug writes: > Is there a particular reason why the "direct" arguments of ordered-set > aggregates are not passed to the transition function too? Because they have to be evaluated only once. I did consider evaluating them once at the start and saving the values, but that's a bit problematic from a memory management standpoint. Still, if you have a good solution to that and the cycles to produce a patch, it's not too late to reconsider. I concur that it's not that hard to think of cases where it'd be useful. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] Passing "direct" args of ordered-set aggs to the transition function
Hi, Is there a particular reason why the "direct" arguments of ordered-set aggregates are not passed to the transition function too? It seems that evaluating of some ordered-set aggregates would be much cheaper if we did that. For example, dense_rank() would then just need to count the number of rows smaller than the hypothetical row, AFAICS. Another example (that we don't currently provide, but still) would be a histogram aggregate which receives an array of buckets as direct args and returns a similarly shaped array of counters. best regards, Florian Pflug -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
