On Thursday, August 14, 2014, Jeff Davis <
pgsql@j-davis.com> wrote:
On Thu, 2014-08-14 at 10:06 -0400, Tom Lane wrote:
> If you're following the HashJoin model, then what you do is the same thing
> it does: you write the input tuple back out to the pending batch file for
> the hash partition that now contains key 1001, whence it will be processed
> when you get to that partition. I don't see that there's any special case
> here.
HashJoin only deals with tuples. With HashAgg, you have to deal with a
mix of tuples and partially-computed aggregate state values. Not
impossible, but it is a little more awkward than HashJoin.
+1
Not to mention future cases if we start maintaining multiple state values,in regarded to grouping sets.
Regards,
Atri
--
Regards,
Atri
l'apprenant