On Thu, Jul 22, 2021 at 9:53 AM Peter Geoghegan <pg@xxxxxxx> wrote: > I suspect David's theory about hash_agg_set_limits()'s ngroup limit is > correct. It certainly seems like a good starting point. I also suspect that if Laurent set work_mem and/or hash_mem_multiplier *extremely* aggressively, then eventually the hash agg would be in-memory. And without actually using all that much memory. I'm not suggesting that that is a sensible resolution to Laurent's complaint. I'm just pointing out that it's probably not fundamentally impossible to make the hash agg avoid spilling through tuning these GUCs. At least I see no evidence of that right now. -- Peter Geoghegan
