Re: Additional size of hash table is alway zero for hash aggregates

>>>>> "Justin" == Justin Pryzby <pryzby@telsasoft.com> writes:

 > On Thu, Mar 12, 2020 at 12:16:26PM -0700, Andres Freund wrote:
 >> Indeed, that's incorrect. Causes the number of buckets for the
 >> hashtable to be set higher - the size is just used for that. I'm a
 >> bit wary of changing this in the stable branches - could cause
 >> performance changes?

I think (offhand, not tested) that the number of buckets would only be
affected if the (planner-supplied) numGroups value would cause work_mem
to be exceeded; the planner doesn't plan a hashagg at all in that case
unless forced to (grouping by a hashable but not sortable column). Note
that for various reasons the planner tends to over-estimate the memory
requirement anyway.