Re: Our trial to TPC-DS but optimizer made unreasonable plan

On Mon, Aug 17, 2015 at 9:40 AM, Kouhei Kaigai <kaigai(at)ak(dot)jp(dot)nec(dot)com> wrote:
> I think SortSupport logic provides a reasonable way to solve this
> kind of problem. For example, btint4sortsupport() informs a function
> pointer of the fast version of comparator (btint4fastcmp) which takes
> two Datum argument without indirect memory reference.
> This mechanism will also make sense for HashAggregate logic, to reduce
> the cost of function invocations.
>
> Please comment on the idea I noticed here.

It's possible that this can work, but it might be a good idea to run
'perf' on this query and find out where the CPU time is actually
going. That might give you a clearer picture of why the HashAggregate
is slow.

--
Robert Haas
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