Re: Memory-Bounded Hash Aggregation

On Fri, 2020-03-27 at 02:31 +0100, Tomas Vondra wrote:
> On Thu, Mar 26, 2020 at 05:56:56PM +0800, Richard Guo wrote:
> > If nbatches is some number between 1.0 and 2.0, we would have a
> > negative
> > depth. As a result, we may have a negative cost for hash
> > aggregation
> > plan node, as described in [1].
> >                 numGroups / ngroups_limit );
> 
> and we should probably do
> 
>    nbatches = ceil(nbatches);
> 

Thank you both. I also protected against nbatches == 0 (shouldn't
happen), and against num_partitions <= 1. That allowed me to remove the
conditional and simplify a bit.

Regards,
    Jeff Davis